Recognize j2k as file suffix for the image2 muxer.

libavformat/img2enc.c

@@ -148,7 +148,7 @@ AVOutputFormat ff_image2_muxer = {
     .name           = "image2",
     .long_name      = NULL_IF_CONFIG_SMALL("image2 sequence"),
     .extensions     = "bmp,dpx,jls,jpeg,jpg,ljpg,pam,pbm,pcx,pgm,pgmyuv,png,"
-                      "ppm,sgi,tga,tif,tiff,jp2,j2c,xwd,sun,ras,rs,im1,im8,im24,"
+                      "ppm,sgi,tga,tif,tiff,jp2,j2c,j2k,xwd,sun,ras,rs,im1,im8,im24,"
                       "sunras,xbm,xface",
     .priv_data_size = sizeof(VideoMuxData),
     .video_codec    = AV_CODEC_ID_MJPEG,