New MD API: rename functions from _ext to _ret

The _ext suffix suggests "new arguments", but the new functions have
the same arguments. Use _ret instead, to convey that the difference is
that the new functions return a value.
diff --git a/programs/hash/hello.c b/programs/hash/hello.c
index a0c08c7..2e8c224 100644
--- a/programs/hash/hello.c
+++ b/programs/hash/hello.c
@@ -54,7 +54,7 @@
 
     mbedtls_printf( "\n  MD5('%s') = ", str );
 
-    if( ( ret = mbedtls_md5_ext( (unsigned char *) str, 13, digest ) ) != 0 )
+    if( ( ret = mbedtls_md5_ret( (unsigned char *) str, 13, digest ) ) != 0 )
         return( MBEDTLS_EXIT_FAILURE );
 
     for( i = 0; i < 16; i++ )
diff --git a/programs/pkey/dh_client.c b/programs/pkey/dh_client.c
index 21c4a81..0978408 100644
--- a/programs/pkey/dh_client.c
+++ b/programs/pkey/dh_client.c
@@ -212,9 +212,9 @@
         goto exit;
     }
 
-    if( ( ret = mbedtls_sha1_ext( buf, (int)( p - 2 - buf ), hash ) ) != 0 )
+    if( ( ret = mbedtls_sha1_ret( buf, (int)( p - 2 - buf ), hash ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_sha1_ext returned %d\n\n", ret );
+        mbedtls_printf( " failed\n  ! mbedtls_sha1_ret returned %d\n\n", ret );
         goto exit;
     }
 
diff --git a/programs/pkey/dh_server.c b/programs/pkey/dh_server.c
index f1d3be3..4d8632b 100644
--- a/programs/pkey/dh_server.c
+++ b/programs/pkey/dh_server.c
@@ -217,9 +217,9 @@
     /*
      * 5. Sign the parameters and send them
      */
-    if( ( ret = mbedtls_sha1_ext( buf, n, hash ) ) != 0 )
+    if( ( ret = mbedtls_sha1_ret( buf, n, hash ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_sha1_ext returned %d\n\n", ret );
+        mbedtls_printf( " failed\n  ! mbedtls_sha1_ret returned %d\n\n", ret );
         goto exit;
     }
 
diff --git a/programs/pkey/ecdsa.c b/programs/pkey/ecdsa.c
index ecb6c22..b474060 100644
--- a/programs/pkey/ecdsa.c
+++ b/programs/pkey/ecdsa.c
@@ -163,9 +163,9 @@
     mbedtls_printf( "  . Computing message hash..." );
     fflush( stdout );
 
-    if( ( ret = mbedtls_sha256_ext( message, sizeof( message ), hash, 0 ) ) != 0 )
+    if( ( ret = mbedtls_sha256_ret( message, sizeof( message ), hash, 0 ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_sha256_ext returned %d\n", ret );
+        mbedtls_printf( " failed\n  ! mbedtls_sha256_ret returned %d\n", ret );
         goto exit;
     }
 
diff --git a/programs/test/benchmark.c b/programs/test/benchmark.c
index 539d9ad..419557d 100644
--- a/programs/test/benchmark.c
+++ b/programs/test/benchmark.c
@@ -327,32 +327,32 @@
 
 #if defined(MBEDTLS_MD4_C)
     if( todo.md4 )
-        TIME_AND_TSC( "MD4", mbedtls_md4_ext( buf, BUFSIZE, tmp ) );
+        TIME_AND_TSC( "MD4", mbedtls_md4_ret( buf, BUFSIZE, tmp ) );
 #endif
 
 #if defined(MBEDTLS_MD5_C)
     if( todo.md5 )
-        TIME_AND_TSC( "MD5", mbedtls_md5_ext( buf, BUFSIZE, tmp ) );
+        TIME_AND_TSC( "MD5", mbedtls_md5_ret( buf, BUFSIZE, tmp ) );
 #endif
 
 #if defined(MBEDTLS_RIPEMD160_C)
     if( todo.ripemd160 )
-        TIME_AND_TSC( "RIPEMD160", mbedtls_ripemd160_ext( buf, BUFSIZE, tmp ) );
+        TIME_AND_TSC( "RIPEMD160", mbedtls_ripemd160_ret( buf, BUFSIZE, tmp ) );
 #endif
 
 #if defined(MBEDTLS_SHA1_C)
     if( todo.sha1 )
-        TIME_AND_TSC( "SHA-1", mbedtls_sha1_ext( buf, BUFSIZE, tmp ) );
+        TIME_AND_TSC( "SHA-1", mbedtls_sha1_ret( buf, BUFSIZE, tmp ) );
 #endif
 
 #if defined(MBEDTLS_SHA256_C)
     if( todo.sha256 )
-        TIME_AND_TSC( "SHA-256", mbedtls_sha256_ext( buf, BUFSIZE, tmp, 0 ) );
+        TIME_AND_TSC( "SHA-256", mbedtls_sha256_ret( buf, BUFSIZE, tmp, 0 ) );
 #endif
 
 #if defined(MBEDTLS_SHA512_C)
     if( todo.sha512 )
-        TIME_AND_TSC( "SHA-512", mbedtls_sha512_ext( buf, BUFSIZE, tmp, 0 ) );
+        TIME_AND_TSC( "SHA-512", mbedtls_sha512_ret( buf, BUFSIZE, tmp, 0 ) );
 #endif
 
 #if defined(MBEDTLS_ARC4_C)