Merge changes I1f0e998b,I39adf4aa,I5b8ea4e2,I02928be0,I75b20025, ... into emu-master-dev

* changes:
  emugl: Simplify RenderChannel interface.
  emugl: Introduce BufferQueue class.
  emugl: ChannelBuffer -> RenderChannel::Buffer
  emugl: put ChannelStream/ReadBuffer/RenderThread in emugl namespace.
  emugl: Move IOStream.h to host/include/libOpenglRender/
  emugl: Add emugl/common/debug.h