MediaInfo: Seek support even if file size computing is disabled

git-svn-id: svn://svn.code.sf.net/p/mediainfo/code/MediaInfoLib/trunk@6577 45c5ae6f-87cc-4fd0-92ee-e4f023fd80da
Optimization of MPEG-TS parsing for low bit rate files

git-svn-id: svn://svn.code.sf.net/p/mediainfo/code/MediaInfoLib/trunk@6578 45c5ae6f-87cc-4fd0-92ee-e4f023fd80da