Add support for DivX XSUB subtitles

Submitted by Bastien Nocera @hadess

Link to original bug (#628429)

Description

Created attachment 169171
test.divx

$ gst-launch playbin2 'uri=file:///home/hadess/Desktop/test.avi'
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
WARNING: from element /GstPlayBin2:playbin20/GstURIDecodeBin:uridecodebin0: No decoder available for type 'video/x-avi-unknown, fourcc=(fourcc)DXSB'.
Additional debug info:
gsturidecodebin.c(712): unknown_type_cb (): /GstPlayBin2:playbin20/GstURIDecodeBin:uridecodebin0
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstPulseSinkClock

The file was created with a "normal" avi file, a corresponding srt file, and AviAddXSUBs1. This is the "supported" way to embed subtitles in DIVX files for use on the PS3, and other "DivX certified" players.

(If the given file isn't good enough, feel free to ask me for another test one)

Attachment 169171, "test.divx":
test.avi