wayland/buffer: Fall back to CoglTexture2DSliced
XWayland creates buffers of the combined size of all connected displays. This can, especially on older but still in use hardware, exceed the limits of the GPU.
If that is the case, use CoglTexture2DSliced
instead of CoglTexture2D
Bonus: small semi-related cleanup in shaped-texture
Fixes #453 (closed)
Edited by Robert Mader