gl-renderer: add support for EGL_KHR_swap_buffers_with_damage

Extension is identical to the EXT one, yet we need to check for the KHR
abbreviated extension name + entry-point.

v2: s/foo/swap_damage_ext_to_entrypoint/ (Eric, Daniel)

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com> (v1)
Reviewed-by: Daniel Stone <daniels@collabora.com>