Revert the new atom changes as they also got reverted later by metacity

Revert "Rename new ATOM from bc8eb8bd2f943b69c87eb7c9e154928f1dd861bb"
This reverts commit 1bd64c3b7eca544f0722cb4c3ee7aa0ca5dd5ec4.

Revert "compositor-xrender: add new atom - METACITY_WINDOW_HAVE_SHADOW"
This reverts commit bc8eb8bd2f943b69c87eb7c9e154928f1dd861bb.