Support H264 over video4linux2.

Tested-by: Val Malykh

libavdevice/v4l2.c

@@ -150,6 +150,9 @@ static struct fmt_map fmt_conversion_table[] = {
     { AV_PIX_FMT_NV12,    AV_CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_NV12    },
     { AV_PIX_FMT_NONE,    AV_CODEC_ID_MJPEG,    V4L2_PIX_FMT_MJPEG   },
     { AV_PIX_FMT_NONE,    AV_CODEC_ID_MJPEG,    V4L2_PIX_FMT_JPEG    },
+#ifdef V4L2_PIX_FMT_H264
+    { AV_PIX_FMT_NONE,    AV_CODEC_ID_H264,     V4L2_PIX_FMT_H264    },
+#endif
 #ifdef V4L2_PIX_FMT_CPIA1
     { AV_PIX_FMT_NONE,    AV_CODEC_ID_CPIA,     V4L2_PIX_FMT_CPIA1   },
 #endif