Add direct link to ML in missing_feature_sample()

Reviewed-by: Clément Bœsch <u@pkh.me>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/utils.c

@@ -3367,7 +3367,7 @@ void av_log_ask_for_sample(void *avc, const char *msg, ...)
         av_vlog(avc, AV_LOG_WARNING, msg, argument_list);
     av_log(avc, AV_LOG_WARNING, "If you want to help, upload a sample "
             "of this file to ftp://upload.ffmpeg.org/MPlayer/incoming/ "
-            "and contact the ffmpeg-devel mailing list.\n");
+            "and contact the ffmpeg-devel mailing list. (ffmpeg-devel@ffmpeg.org)\n");
 
     va_end(argument_list);
 }