Fix missing include in some files

Add it in all files that use mbedtls_plaform_memset() but didn't already
include platfom_util.h.

In some configurations it just happened to work, either because it was
included indirectly or because the part of the code that used that function
was disabled, but it some configurations it broke, so let's fix it properly.
diff --git a/library/debug.c b/library/debug.c
index 9c8c2f6..a55324e 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -42,6 +42,7 @@
 #include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
+#include "mbedtls/platform_util.h"
 
 #if ( defined(__ARMCC_VERSION) || defined(_MSC_VER) ) && \
     !defined(inline) && !defined(__cplusplus)
diff --git a/library/entropy_poll.c b/library/entropy_poll.c
index 413be4a..1fe4e81 100644
--- a/library/entropy_poll.c
+++ b/library/entropy_poll.c
@@ -31,6 +31,7 @@
 #endif
 
 #include <string.h>
+#include "mbedtls/platform_util.h"
 
 #if defined(MBEDTLS_ENTROPY_C)
 
diff --git a/library/error.c b/library/error.c
index 5a813f1..c993524 100644
--- a/library/error.c
+++ b/library/error.c
@@ -28,6 +28,7 @@
 #if defined(MBEDTLS_ERROR_C) || defined(MBEDTLS_ERROR_STRERROR_DUMMY)
 #include "mbedtls/error.h"
 #include <string.h>
+#include "mbedtls/platform_util.h"
 #endif
 
 #if defined(MBEDTLS_PLATFORM_C)
diff --git a/library/net_sockets.c b/library/net_sockets.c
index 58244e5..76b0ecd 100644
--- a/library/net_sockets.c
+++ b/library/net_sockets.c
@@ -47,6 +47,7 @@
 #include "mbedtls/net_sockets.h"
 
 #include <string.h>
+#include "mbedtls/platform_util.h"
 
 #if (defined(_WIN32) || defined(_WIN32_WCE)) && !defined(EFIX64) && \
     !defined(EFI32)
diff --git a/library/pkcs11.c b/library/pkcs11.c
index ecdfde9..7bbc555 100644
--- a/library/pkcs11.c
+++ b/library/pkcs11.c
@@ -40,6 +40,7 @@
 #endif
 
 #include <string.h>
+#include "mbedtls/platform_util.h"
 
 void mbedtls_pkcs11_init( mbedtls_pkcs11_context *ctx )
 {
diff --git a/library/pkcs5.c b/library/pkcs5.c
index e551547..7580da7 100644
--- a/library/pkcs5.c
+++ b/library/pkcs5.c
@@ -46,6 +46,7 @@
 #endif /* MBEDTLS_ASN1_PARSE_C */
 
 #include <string.h>
+#include "mbedtls/platform_util.h"
 
 #if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
diff --git a/library/ssl_cache.c b/library/ssl_cache.c
index fefc6d0..36c4398 100644
--- a/library/ssl_cache.c
+++ b/library/ssl_cache.c
@@ -43,6 +43,7 @@
 #include "mbedtls/ssl_internal.h"
 
 #include <string.h>
+#include "mbedtls/platform_util.h"
 
 void mbedtls_ssl_cache_init( mbedtls_ssl_cache_context *cache )
 {