ClutterBox is meant to work like the HTML boxing model: it has a margin and
a backgrdound color, and every child actor is added with a pack type and a
padding. The ClutterBoxChild structure holds the child actor, the padding,
the packing type and the allocated coordinates for the actor.
Most of these fixes are simple symbol shadowing issues, like index and the
braindead y0 and y1 extern symbols exported by math.h on GNU libc systems.
There is a masking issue in ClutterTexture which should be checked; I ran
the tests and everything looked fine.
The rest are just unused variables.
