Use COGL_FLAGS_* for the context's private feature flags

Previously the private feature flags were stored in an enum and we
already had 31 flags. Adding the 32nd flag would presumably make it
add -2³¹ as one of the values which might cause problems. To avoid
this we'll just use an fixed-size array of longs and use indices for
the enum values like we do for the public features.

A slight complication with this is in the CoglDriverDescription where
we were previously using a static intialised value to describe the set
of features that the driver supports. We can't easily do this with the
flags array so instead the features are stored in a fixed-size array
of indices.

Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit d94cb984e3c93630f3c2e6e3be9d189672aa20f3)

Conflicts:
	cogl/cogl-context-private.h
	cogl/cogl-context.c
	cogl/cogl-private.h
	cogl/cogl-renderer.c
	cogl/driver/gl/cogl-pipeline-opengl.c
	cogl/driver/gl/gl/cogl-driver-gl.c
	cogl/driver/gl/gl/cogl-pipeline-progend-fixed-arbfp.c
	cogl/driver/gl/gles/cogl-driver-gles.c
	cogl/driver/nop/cogl-driver-nop.c
Revert "cogl-texture-2d: Add update_area equivalent for Wayland"

This patch was accidentally added before it had any review and without
first going through master. Master now has a replacement patch with
some modifications. That will be cherry-picked to the 1.18 branch in a
subsequent commit.

This reverts commit af480a2b8b5450148ca4b969eec90ee330d5fd12.
wayland: Add a convenience function to update a region from SHM buffer

Adds cogl_wayland_texture_set_region_from_shm_buffer which is a
convenience wrapper around cogl_texture_set_region but it uses the
correct format to copy the data from a Wayland SHM buffer. This will
typically be used by compositors to update the texture for a surface
when an SHM buffer is attached. The ordering of the arguments is based
on cogl_texture_set_region_from_bitmap.

Based on a patch by Jasper St. Pierre.

Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit c76c1d136d2cac7f3d1331a4d1dc0dd0f06e812c)

Conflicts:
	examples/cogland.c