To help facilitate integration with third party frameworks this exposes
the EGL context and display to applications as well as the GLX context.
(Note that the GLX display is already available via
cogl_xlib_renderer_get_display())
This adds a new top-level <cogl/cogl-glx.h> header that needs to be
included explicitly to access the glx specific api.
Anyone using these apis will be responsible for checking that Cogl
is indeed using EGL or GLX by calling cogl_renderer_get_winsys_id()
This will enable GStreamer, for example, to be able to create a GL
context that shares resources with Cogl's context.
https://bugzilla.gnome.org/show_bug.cgi?id=724992
Reviewed-by: Neil Roberts <neil@linux.intel.com>
