[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.