avformat: allow .264 as extension for raw H.264 stream

In addition to .h264, .264 is also commonly used by people to name raw H.264
streams. Enables automatic recognition of the h264 format for the .264
extension.
Signed-off-by: Werner Robitza <werner.robitza@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/rawenc.c

@@ -205,7 +205,7 @@ AVOutputFormat ff_h263_muxer = {
 AVOutputFormat ff_h264_muxer = {
     .name              = "h264",
     .long_name         = NULL_IF_CONFIG_SMALL("raw H.264 video"),
-    .extensions        = "h264",
+    .extensions        = "h264,264",
     .audio_codec       = AV_CODEC_ID_NONE,
     .video_codec       = AV_CODEC_ID_H264,
     .write_header      = force_one_stream,