Add av_printf_format, for marking printf style format strings and their parameters

Signed-off-by: Martin Storsjö <martin@martin.st>

doc/APIchanges

@@ -13,6 +13,9 @@ libavutil:   2011-04-18
 
 API changes, most recent first:
 
+2011-06-xx - xxxxxxx - lavu 51.8.0 - attributes.h
+  Add av_printf_format().
+
 2011-06-xx - xxxxxxx - lavf 53.2.0 - avformat.h
   Add avformat_open_input and avformat_write_header().
   Deprecate av_open_input_stream, av_open_input_file,

libavutil/attributes.h

@@ -127,8 +127,10 @@
 
 #ifdef __GNUC__
 #    define av_builtin_constant_p __builtin_constant_p
+#    define av_printf_format(fmtpos, attrpos) __attribute__((__format__(__printf__, fmtpos, attrpos)))
 #else
 #    define av_builtin_constant_p(x) 0
+#    define av_printf_format(fmtpos, attrpos)
 #endif
 
 #endif /* AVUTIL_ATTRIBUTES_H */

libavutil/avutil.h

@@ -40,7 +40,7 @@
 #define AV_VERSION(a, b, c) AV_VERSION_DOT(a, b, c)
 
 #define LIBAVUTIL_VERSION_MAJOR 51
-#define LIBAVUTIL_VERSION_MINOR  7
+#define LIBAVUTIL_VERSION_MINOR  8
 #define LIBAVUTIL_VERSION_MICRO  0
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \