This makes it easier for userspace to know when it needs to allocate an ID.
Also free drawable information memory when it's no longer needed.
(cherry picked from df7551ef73 commit)
Actually make the existing ioctls for adding and removing drawables do
something useful, and add another ioctl for the X server to update drawable
information. The only kind of drawable information tracked so far is cliprects.
(cherry picked from 29598e5253 commit)
Michel Dänzer