Revert "Revert "Remove the framebuffer's stack of clip stacks""

This reverts commit bc4148933670cea024cf7525b58bfa673898ec75.

The reason this was causing problems for Clutter is that it defines
COGL_ENABLE_EXPERIMENTAL_2_0_API which is meant to cause the Cogl
headers not to declare the deprecated API. The reverted patch moved
some additional clipping API to a deprecated header which was
previously being used by Clutter. Clutter was still successfully
compiling but with some warnings for the missing function
declarations. However when the binary is run the clipping would get
completely messed up because it would assume all of the arguments to
the functions are integers instead of floats and the wrong values
would be passed.

Clutter now has commit to make it use the 2.0 API instead of the
deprecated functions so the revert is no longer necessary.

https://git.gnome.org/browse/clutter/commit?id=705640367a5c2ae21405806bfa

Reviewed-by: Robert Bragg <robert@linux.intel.com>