Fix compilation error with Mingw32

Fix compilation error on Mingw32 when `_TRUNCATE` is defined. Use
`_TRUNCATE` only if `__MINGW32__` not defined. Fix suggested by
Thomas Glanzmann and Nick Wilson on issue #355
diff --git a/ChangeLog b/ChangeLog
index ed7818e..80d4cf5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -62,6 +62,9 @@
    * Fix issue in RSA key generation program programs/x509/rsa_genkey
      where the failure of CTR DRBG initialization lead to freeing an
      RSA context without proper initialization beforehand.
+   * Fix compilation error on Mingw32 when `_TRUNCATE` is defined. Use `_TRUNCATE`
+     only if `__MINGW32__` not defined. Fix suggested by Thomas Glanzmann and
+     Nick Wilson on issue #355
 
 Changes
    * Extend cert_write example program by options to set the CRT version
diff --git a/library/debug.c b/library/debug.c
index 4752ab1..afa21cb 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -90,7 +90,7 @@
 
     va_start( argp, format );
 #if defined(_WIN32)
-#if defined(_TRUNCATE)
+#if defined(_TRUNCATE) && !defined(__MINGW32__)
     ret = _vsnprintf_s( str, DEBUG_BUF_SIZE, _TRUNCATE, format, argp );
 #else
     ret = _vsnprintf( str, DEBUG_BUF_SIZE, format, argp );
diff --git a/library/platform.c b/library/platform.c
index d634c62..e90dc3c 100644
--- a/library/platform.c
+++ b/library/platform.c
@@ -74,7 +74,7 @@
         return( -1 );
 
     va_start( argp, fmt );
-#if defined(_TRUNCATE)
+#if defined(_TRUNCATE) && !defined(__MINGW32__)
     ret = _vsnprintf_s( s, n, _TRUNCATE, fmt, argp );
 #else
     ret = _vsnprintf( s, n, fmt, argp );