Cogland works a lot better with an EGL context because then Mesa will
automatically set up the wl_drm object and it can accept DRM buffers.
However Cogland is still useful with GLX because it can gracefully
fallback to accepting only SHM buffers. This patch therefore makes it
first try creating and connecting a renderer with the EGL constraint,
but if that doesn't work it will try again without it.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 05ddc7d75e77538b5de22d4336d4a444d122063b)
856e9aa5f4
