Fix build with Visual C++ and /std:c11 or /std:c17

Fixes #481
Closes #482
diff --git a/tjutil.h b/tjutil.h
index f72840c..8542bab 100644
--- a/tjutil.h
+++ b/tjutil.h
@@ -30,7 +30,7 @@
 #ifndef __MINGW32__
 #include <stdio.h>
 #define snprintf(str, n, format, ...) \
-  _snprintf_s(str, n, _TRUNCATE, format, __VA_ARGS__)
+  _snprintf_s(str, n, _TRUNCATE, format, ##__VA_ARGS__)
 #endif
 #define strcasecmp  stricmp
 #define strncasecmp  strnicmp