Add printf attribute to asprintf

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@118328 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/compat.h

@@ -74,7 +74,7 @@
 #endif
 
 #if !defined(HAVE_ASPRINTF) && !defined(__AST_DEBUG_MALLOC)
-int asprintf(char **str, const char *fmt, ...);
+int __attribute__ ((format (printf, 2, 3))) asprintf(char **str, const char *fmt, ...);
 #endif
 
 #ifndef HAVE_GETLOADAVG