tests: avoid MSVC preaching about unsafe functions

test/testiconv.c

@@ -10,6 +10,11 @@
   freely.
 */
 
+/* quiet windows compiler warnings */
+#if defined(_MSC_VER) && !defined(_CRT_SECURE_NO_WARNINGS)
+# define _CRT_SECURE_NO_WARNINGS
+#endif
+
 #include <stdio.h>
 
 #include "SDL.h"