matroskaenc: correct muxing of ASS packets  - split packets to store one ASS event line per Matroska block  - reformat ASS events to Matroska modified format  - extract display duration for ASS events to store as Matroska block duration
matroskaenc: correct muxing of ASS packets
 - split packets to store one ASS event line per Matroska block
 - reformat ASS events to Matroska modified format
 - extract display duration for ASS events to store as Matroska block duration


git-svn-id: a4d7c1866f8397a4106e0b57fc4fbf792bbdaaaf@15561 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg