[compiz] change how vertices are generated

[David Reveman]

We need to change the way vertices are generated for windows. We
currently have a addWindowGeometry screen function that takes care of
this. It can be wrapped by plugins and it can generate any vertices and
texture coordinates it wants.

I'd like to change it so that the region for which to generate vertices
and texture coordinates will be specified elsewhere and it doesn't have
to be constrained to the dimensions of the texture.

The reason for this is that when adding support for input
transformations we need to be able to transform not only the coordinates
within the visible part of the window but any coordinate that can be
reported in events that are generated with respect to the window.

Another thing that we need to changed is the way animations are
initiated and performed. Plugins are currently sort of hijacking the
addWindowGeometry function when they feel appropriate without the code
that initiated the animation knowing anything about it. A better model
would be to have the code that can cause an animation to happen also be
the code that initiates the animation. E.g. instead of having the wobbly
plugin deform the window geometry while the move plugin is moving a
window, the move plugin should initiate an animation object and be
responsible for making the animation advance.

- David