Remove unused Wayland includes
monitor: Don't use wl_output_transform in our APIs

Invent our own API so we can build without Wayland headers.
display: Use a local here instead of the global the_display

This will make it easier to split some of this functionality out into
other subfunctions.
display: Add an extra check inside meta_display_close

For clarity of what the expected input to this function is.
events: Return early if we close the display

This is so we won't poke into the MetaDisplay, which is invalid memory,
and crash. This can sometimes work right now because GSlice might not
deallocate the object immediately, but it's still not a fun thing to do.
Makefile: Disable Clutter / Cogl deprecation warnings

These just spam up our logs, and they aren't getting fixed any time
soon for a variety of reasons. Just disable them to ensure that really
important warnings get noticed and fixed.