Merge branch 'master' of https://github.com/Infatum/stb into dev

stb.h

@@ -193,6 +193,8 @@ CREDITS
   Tim Sjostrand
 */
 
+#include <stdarg.h>
+
 #ifndef STB__INCLUDE_STB_H
 #define STB__INCLUDE_STB_H
 

stb_vorbis.c

@@ -577,6 +577,7 @@ enum STBVorbisError
    #undef __forceinline
    #endif
    #define __forceinline
+#define alloca __builtin_alloca
 #elif !defined(_MSC_VER)
    #if __GNUC__
       #define __forceinline inline