[mythtv-cmyth] Demuxing MPEG-TS

- Handles demuxing MPEG-TS for liveTV
New setting 'demuxing' in category 'advanced' allows to enable/disable the fonctionality.

- Includes tool for testing
Provides demuxer/Makefile to build 'test_demux'
[mythtv-cmyth] API 1.9.0

Implements timeshift functions
- GetPlayingTime()
  Available only using internal demuxing MPEG-TS, else default value will be returned to PVR.

- GetBufferStartTime()
  Returns start time of first recording in the liveTV chain.

- GetBufferEndTime()
  Returns least of current time and end time of last recording in the liveTV chain.
[mythtv-cmyth] Demuxing MPEG-TS: Use codec name 'eac3' for DVB enhanced AC3
[mythtv-cmyth] Demuxing MPEG-TS: Fix unsupported language codes

- While XBMC does'nt support them
  Fix unsupported language codes (EN 300 468 Annex F & J)
  'qaa': Original audio
  'qad','NAR': Audio Description

Static function recode_language() do the work
[mythtv-cmyth] Demuxing MPEG-TS: Handling invalid seek from PVR

- Handles invalid request which break seek flow
- Handles PTS discontinuity on program break
- Add extra logs for debug