Include MinGW in the non-conforming (v)snprintf scope

It turns out that in some environments MinGW esposes a non-conforming
(v)snprintf behavior despite the tests against the MSVC runtime pass.
Therefore it has been included in the "non-conforming" scope alongide
older MSVC rungime environments.
diff --git a/include/mbedtls/platform.h b/include/mbedtls/platform.h
index ada898e..afd6367 100644
--- a/include/mbedtls/platform.h
+++ b/include/mbedtls/platform.h
@@ -59,7 +59,7 @@
  * implementations of some standard library functions, including snprintf
  * and vsnprintf. This affects MSVC and MinGW builds.
  */
-#if defined(_MSC_VER) && _MSC_VER <= 1900
+#if defined(__MINGW32__) || (defined(_MSC_VER) && _MSC_VER <= 1900)
 #define MBEDTLS_PLATFORM_HAS_NON_CONFORMING_SNPRINTF
 #define MBEDTLS_PLATFORM_HAS_NON_CONFORMING_VSNPRINTF
 #endif
diff --git a/library/platform.c b/library/platform.c
index 8bf6ff5..4f8e40f 100644
--- a/library/platform.c
+++ b/library/platform.c
@@ -30,10 +30,6 @@
 #include "mbedtls/platform.h"
 #include "mbedtls/platform_util.h"
 
-#if defined(__MINGW32__) && !defined(__USE_MINGW_ANSI_STDIO)
-#define __USE_MINGW_ANSI_STDIO 1
-#endif
-
 #if defined(MBEDTLS_PLATFORM_MEMORY)
 #if !defined(MBEDTLS_PLATFORM_STD_CALLOC)
 static void *platform_calloc_uninit( size_t n, size_t size )