Support EGLStream video streaming on QNX platform

On QNX platform, we implement video streaming via OpenGL
EGLStream streams. Changes were added to StreamVideo class
to support EGLStream objects. For non-QNX platforms, we
kept the StreamVideoNode class unchanged - assuming other
platforms will continue to support streaming via EGLImage
objects.

On QNX, cc::StreamVideoDrawQuad contains an
external OES texture that is associated with an
EGLStream. Before we draw with that texture, an
'acquire' is performed to grab latest video frame.
See EGL_KHR_stream specs from Khronos.

Change-Id: Ia3fe25e9047f475594a55591e3e11caa0eab1e6a
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>