wayland-server: Update because wl_shm_buffer is no longer a wl_buffer

The Wayland server API has changed so that wl_shm_buffer is no longer
a type of wl_buffer and it instead must be retrieved directly from the
resource.

cogl_wayland_texture_2d_new_from_buffer now takes a resource pointer
instead of directly taking a wl_buffer and it will do different things
depending on whether it can get a wl_shm_buffer out of the resource
instead of trying to query the buffer type.

Cogland has also been updated so that it tracks a resource for buffers
of surfaces instead of directly tracking a wl_buffer. This are pointed
to by a new CoglandBuffer struct which can be referenced by a
CoglandBufferReference. The WL_BUFFER_RELEASE event will be posted
when the last reference to the buffer is removed instead of directly
whenever a new buffer is attached. This is similar to how Weston
works.

https://bugzilla.gnome.org/show_bug.cgi?id=702999



Reviewed-by: Robert Bragg <robert@linux.intel.com>