Unify the example programs' termination

This is done to account for platforms, for which we want custom behavior
upon the program termination, hence we call `mbedtls_exit()` instead of
returning from `main()`.

For the sake of consistency, introduces the modifications have been made
to the test and utility examples as well. These, while less likely to be
used in the low level environments, won't suffer from such a change.
diff --git a/programs/ssl/dtls_client.c b/programs/ssl/dtls_client.c
index c29ab34..b72981c 100644
--- a/programs/ssl/dtls_client.c
+++ b/programs/ssl/dtls_client.c
@@ -29,8 +29,10 @@
 #include "mbedtls/platform.h"
 #else
 #include <stdio.h>
+#include <stdlib.h>
 #define mbedtls_printf     printf
 #define mbedtls_fprintf    fprintf
+#define mbedtls_exit       exit
 #endif
 
 #if !defined(MBEDTLS_SSL_CLI_C) || !defined(MBEDTLS_SSL_PROTO_DTLS) ||    \
@@ -45,7 +47,7 @@
             "MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C and/or "
             "MBEDTLS_X509_CRT_PARSE_C and/or MBEDTLS_RSA_C and/or "
             "MBEDTLS_CERTS_C and/or MBEDTLS_PEM_PARSE_C not defined.\n" );
-    return( 0 );
+    mbedtls_exit( 0 );
 }
 #else
 
@@ -351,7 +353,7 @@
     if( ret < 0 )
         ret = 1;
 
-    return( ret );
+    mbedtls_exit( ret );
 }
 #endif /* MBEDTLS_SSL_CLI_C && MBEDTLS_SSL_PROTO_DTLS && MBEDTLS_NET_C &&
           MBEDTLD_TIMING_C && MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C &&
diff --git a/programs/ssl/dtls_server.c b/programs/ssl/dtls_server.c
index b4ad6b5..9a9574f 100644
--- a/programs/ssl/dtls_server.c
+++ b/programs/ssl/dtls_server.c
@@ -29,9 +29,11 @@
 #include "mbedtls/platform.h"
 #else
 #include <stdio.h>
+#include <stdlib.h>
 #define mbedtls_printf     printf
 #define mbedtls_fprintf    fprintf
 #define mbedtls_time_t     time_t
+#define mbedtls_exit       exit
 #endif
 
 /* Uncomment out the following line to default to IPv4 and disable IPv6 */
@@ -58,7 +60,7 @@
             "MBEDTLS_X509_CRT_PARSE_C and/or MBEDTLS_RSA_C and/or "
             "MBEDTLS_CERTS_C and/or MBEDTLS_PEM_PARSE_C and/or "
             "MBEDTLS_TIMING_C not defined.\n" );
-    return( 0 );
+    mbedtls_exit( 0 );
 }
 #else
 
@@ -426,7 +428,7 @@
     if( ret < 0 )
         ret = 1;
 
-    return( ret );
+    mbedtls_exit( ret );
 }
 #endif /* MBEDTLS_SSL_SRV_C && MBEDTLS_SSL_PROTO_DTLS &&
           MBEDTLS_SSL_COOKIE_C && MBEDTLS_NET_C && MBEDTLS_ENTROPY_C &&
diff --git a/programs/ssl/mini_client.c b/programs/ssl/mini_client.c
index 290455e..6db0461 100644
--- a/programs/ssl/mini_client.c
+++ b/programs/ssl/mini_client.c
@@ -26,6 +26,15 @@
 #include MBEDTLS_CONFIG_FILE
 #endif
 
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#include <stdio.h>
+#include <stdlib.h>
+#define mbedtls_printf printf
+#define mbedtls_exit   exit
+#endif
+
 /*
  * We're creating and connecting the socket "manually" rather than using the
  * NET module, in order to avoid the overhead of getaddrinfo() which tends to
@@ -44,28 +53,15 @@
     !defined(MBEDTLS_NET_C) || !defined(MBEDTLS_SSL_CLI_C) || \
     !defined(UNIX)
 
-#if defined(MBEDTLS_PLATFORM_C)
-#include "mbedtls/platform.h"
-#else
-#include <stdio.h>
-#define mbedtls_printf printf
-#endif
-
 int main( void )
 {
     mbedtls_printf( "MBEDTLS_CTR_DRBG_C and/or MBEDTLS_ENTROPY_C and/or "
             "MBEDTLS_NET_C and/or MBEDTLS_SSL_CLI_C and/or UNIX "
             "not defined.\n");
-    return( 0 );
+    mbedtls_exit( 0 );
 }
 #else
 
-#if defined(MBEDTLS_PLATFORM_C)
-#include "mbedtls/platform.h"
-#else
-#include <stdlib.h>
-#endif
-
 #include <string.h>
 
 #include "mbedtls/net_sockets.h"
@@ -297,6 +293,6 @@
     mbedtls_x509_crt_free( &ca );
 #endif
 
-    return( ret );
+    mbedtls_exit( ret );
 }
 #endif
diff --git a/programs/ssl/ssl_client1.c b/programs/ssl/ssl_client1.c
index bf7c013..142f4d4 100644
--- a/programs/ssl/ssl_client1.c
+++ b/programs/ssl/ssl_client1.c
@@ -34,6 +34,7 @@
 #define mbedtls_time_t          time_t
 #define mbedtls_fprintf         fprintf
 #define mbedtls_printf          printf
+#define mbedtls_exit            exit
 #define MBEDTLS_EXIT_SUCCESS    EXIT_SUCCESS
 #define MBEDTLS_EXIT_FAILURE    EXIT_FAILURE
 #endif /* MBEDTLS_PLATFORM_C */
@@ -50,7 +51,7 @@
            "MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
            "MBEDTLS_CTR_DRBG_C and/or MBEDTLS_X509_CRT_PARSE_C "
            "not defined.\n");
-    return( 0 );
+    mbedtls_exit( 0 );
 }
 #else
 
@@ -310,7 +311,7 @@
     fflush( stdout ); getchar();
 #endif
 
-    return( exit_code );
+    mbedtls_exit( exit_code );
 }
 #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_SSL_TLS_C &&
           MBEDTLS_SSL_CLI_C && MBEDTLS_NET_C && MBEDTLS_RSA_C &&
diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index c63c4f7..58e6d7e 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -35,6 +35,7 @@
 #define mbedtls_printf     printf
 #define mbedtls_fprintf    fprintf
 #define mbedtls_snprintf   snprintf
+#define mbedtls_exit       exit
 #endif
 
 #if !defined(MBEDTLS_ENTROPY_C) || \
@@ -45,7 +46,7 @@
     mbedtls_printf("MBEDTLS_ENTROPY_C and/or "
            "MBEDTLS_SSL_TLS_C and/or MBEDTLS_SSL_CLI_C and/or "
            "MBEDTLS_NET_C and/or MBEDTLS_CTR_DRBG_C and/or not defined.\n");
-    return( 0 );
+    mbedtls_exit( 0 );
 }
 #else
 
@@ -1838,7 +1839,7 @@
     if( ret < 0 )
         ret = 1;
 
-    return( ret );
+    mbedtls_exit( ret );
 }
 #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_SSL_TLS_C &&
           MBEDTLS_SSL_CLI_C && MBEDTLS_NET_C && MBEDTLS_RSA_C &&
diff --git a/programs/ssl/ssl_fork_server.c b/programs/ssl/ssl_fork_server.c
index 1c3a806..7b98263 100644
--- a/programs/ssl/ssl_fork_server.c
+++ b/programs/ssl/ssl_fork_server.c
@@ -33,6 +33,7 @@
 #define mbedtls_fprintf         fprintf
 #define mbedtls_printf          printf
 #define mbedtls_time_t          time_t
+#define mbedtls_exit            exit
 #define MBEDTLS_EXIT_SUCCESS    EXIT_SUCCESS
 #define MBEDTLS_EXIT_FAILURE    EXIT_FAILURE
 #endif /* MBEDTLS_PLATFORM_C */
@@ -53,14 +54,14 @@
            "MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
            "MBEDTLS_CTR_DRBG_C and/or MBEDTLS_X509_CRT_PARSE_C and/or "
            "MBEDTLS_TIMING_C and/or MBEDTLS_PEM_PARSE_C not defined.\n");
-    return( 0 );
+    mbedtls_exit( 0 );
 }
 #elif defined(_WIN32)
 int main( void )
 {
     mbedtls_printf("_WIN32 defined. This application requires fork() and signals "
            "to work correctly.\n");
-    return( 0 );
+    mbedtls_exit( 0 );
 }
 #else
 
@@ -414,7 +415,7 @@
     fflush( stdout ); getchar();
 #endif
 
-    return( exit_code );
+    mbedtls_exit( exit_code );
 }
 #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_CERTS_C && MBEDTLS_ENTROPY_C &&
           MBEDTLS_SSL_TLS_C && MBEDTLS_SSL_SRV_C && MBEDTLS_NET_C &&
diff --git a/programs/ssl/ssl_mail_client.c b/programs/ssl/ssl_mail_client.c
index 8ec6079..086469d 100644
--- a/programs/ssl/ssl_mail_client.c
+++ b/programs/ssl/ssl_mail_client.c
@@ -34,6 +34,7 @@
 #define mbedtls_time_t          time_t
 #define mbedtls_fprintf         fprintf
 #define mbedtls_printf          printf
+#define mbedtls_exit            exit
 #define MBEDTLS_EXIT_SUCCESS    EXIT_SUCCESS
 #define MBEDTLS_EXIT_FAILURE    EXIT_FAILURE
 #endif /* MBEDTLS_PLATFORM_C */
@@ -50,7 +51,7 @@
            "MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
            "MBEDTLS_CTR_DRBG_C and/or MBEDTLS_X509_CRT_PARSE_C "
            "not defined.\n");
-    return( 0 );
+    mbedtls_exit( 0 );
 }
 #else
 
@@ -846,7 +847,7 @@
     fflush( stdout ); getchar();
 #endif
 
-    return( exit_code );
+    mbedtls_exit( exit_code );
 }
 #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_SSL_TLS_C &&
           MBEDTLS_SSL_CLI_C && MBEDTLS_NET_C && MBEDTLS_RSA_C **
diff --git a/programs/ssl/ssl_pthread_server.c b/programs/ssl/ssl_pthread_server.c
index 9a05ad8..b51bea6 100644
--- a/programs/ssl/ssl_pthread_server.c
+++ b/programs/ssl/ssl_pthread_server.c
@@ -30,9 +30,11 @@
 #include "mbedtls/platform.h"
 #else
 #include <stdio.h>
+#include <stdlib.h>
 #define mbedtls_fprintf    fprintf
 #define mbedtls_printf     printf
 #define mbedtls_snprintf   snprintf
+#define mbedtls_exit       exit
 #endif
 
 #if !defined(MBEDTLS_BIGNUM_C) || !defined(MBEDTLS_CERTS_C) ||            \
@@ -50,7 +52,7 @@
            "MBEDTLS_CTR_DRBG_C and/or MBEDTLS_X509_CRT_PARSE_C and/or "
            "MBEDTLS_THREADING_C and/or MBEDTLS_THREADING_PTHREAD "
            "and/or MBEDTLS_PEM_PARSE_C not defined.\n");
-    return( 0 );
+    mbedtls_exit( 0 );
 }
 #else
 
@@ -520,7 +522,7 @@
     fflush( stdout ); getchar();
 #endif
 
-    return( ret );
+    mbedtls_exit( ret );
 }
 
 #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_CERTS_C && MBEDTLS_ENTROPY_C &&
diff --git a/programs/ssl/ssl_server.c b/programs/ssl/ssl_server.c
index dcdafbb..72a0c6a 100644
--- a/programs/ssl/ssl_server.c
+++ b/programs/ssl/ssl_server.c
@@ -34,6 +34,7 @@
 #define mbedtls_time_t     time_t
 #define mbedtls_fprintf    fprintf
 #define mbedtls_printf     printf
+#define mbedtls_exit            exit
 #endif
 
 #if !defined(MBEDTLS_BIGNUM_C) || !defined(MBEDTLS_CERTS_C) ||    \
@@ -49,7 +50,7 @@
            "MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
            "MBEDTLS_CTR_DRBG_C and/or MBEDTLS_X509_CRT_PARSE_C "
            "and/or MBEDTLS_PEM_PARSE_C not defined.\n");
-    return( 0 );
+    mbedtls_exit( 0 );
 }
 #else
 
@@ -393,7 +394,7 @@
     fflush( stdout ); getchar();
 #endif
 
-    return( ret );
+    mbedtls_exit( ret );
 }
 #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_CERTS_C && MBEDTLS_ENTROPY_C &&
           MBEDTLS_SSL_TLS_C && MBEDTLS_SSL_SRV_C && MBEDTLS_NET_C &&
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index ae57f1f..1d439f1 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -33,9 +33,10 @@
 #define mbedtls_free       free
 #define mbedtls_time       time
 #define mbedtls_time_t     time_t
-#define mbedtls_calloc    calloc
+#define mbedtls_calloc     calloc
 #define mbedtls_fprintf    fprintf
 #define mbedtls_printf     printf
+#define mbedtls_exit       exit
 #endif
 
 #if !defined(MBEDTLS_ENTROPY_C) || \
@@ -46,7 +47,7 @@
     mbedtls_printf("MBEDTLS_ENTROPY_C and/or "
            "MBEDTLS_SSL_TLS_C and/or MBEDTLS_SSL_SRV_C and/or "
            "MBEDTLS_NET_C and/or MBEDTLS_CTR_DRBG_C and/or not defined.\n");
-    return( 0 );
+    mbedtls_exit( 0 );
 }
 #else
 
@@ -2583,7 +2584,7 @@
     if( ret < 0 )
         ret = 1;
 
-    return( ret );
+    mbedtls_exit( ret );
 }
 #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_SSL_TLS_C &&
           MBEDTLS_SSL_SRV_C && MBEDTLS_NET_C && MBEDTLS_RSA_C &&