* replacing calls to not-always-available gmtime_r with our own code.

The new helper function actually differs in semantics from gmtime_r,
     so if that seems to be a problem I can actually move it to dv.c
     completely, since only DV muxer uses the code anyway.

Originally committed as revision 3399 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/avformat.h

@@ -620,6 +620,7 @@ do {\
 #endif
 
 time_t mktimegm(struct tm *tm);
+struct tm *brktimegm(time_t secs, struct tm *tm);
 const char *small_strptime(const char *p, const char *fmt, 
                            struct tm *dt);