Bug 885 - GLMediaPlayer: Allow single threaded mode - Especially where multiple media textures (Android) or shared GL context are not usable.

- GLMediaPlayer:
  - TEXTURE_COUNT_MIN is the new minimum: '1' - i.e. no multithreading, single threaded player
  - TEXTURE_COUNT_DEFAULT is '4' - multithreaded

- GLMediaPlayerImpl:
  - Add Single threaded mode, but perform initStreamImpl(..) off-thread.
  -
GLRendererQuirks: Add GLSharedContextBuggy ('Mesa Intel 9.2.1' and 'Hisilicon Immersion.16')

Note: Even though Mesa Intel driver crashes w/ heavy multithreading (Bug 873),
it works well w/ our multithreaded GLMediaPlayer.