Fix generation of Mono Glue for Visual Studio 2017+

vsnprintf definition should only be changed when MSC version is older than 2013. The version check and fix is taken from StringUtils.h of assimp.

modules/mono/utils/string_utils.cpp

@@ -210,7 +210,7 @@ String str_format(const char *p_format, ...) {
 #endif
 #endif
 
-#if defined(MINGW_ENABLED) || defined(_MSC_VER)
+#if defined(MINGW_ENABLED) || defined(_MSC_VER) && _MSC_VER < 1900
 #define vsnprintf(m_buffer, m_count, m_format, m_argptr) vsnprintf_s(m_buffer, m_count, _TRUNCATE, m_format, m_argptr)
 #endif