Replace get_native API
In !107 (merged) I added get_native
functions to the surfaceless backend and removed a comment that describes a future improvement. I'm filing this issue so we don't forget about the idea:
// [chadv] I regret the design of the get_native interface, and wish to
// deprecate and replace it with the interface that Ian Romanick orignally
// recommended: waffle_display_get_egl_display(),
// waffle_display_get_gbm_device(), waffle_display_get_xlib_display(), etc. As
// a first step towards that goal, I choose to not support the interface on new
// platforms.