composite: Fix wording a tiny bit
demos: Fix a tiny code error
class: Fix some error conditions when using parent()
cm: Split out the default Canvas2D renderer

We'll soon add a WebGL-based one.
cm: Add a hook for Damage events

We'll use this in the GL renderer to dirty images for a new upload.
cm: Add a simple WebGL-based compositor
pixman-region-wrapper: Remove unused methods
pixman-region-wrapper: Change the iter_rectangles callback slightly

We're almost ready to replace the Pixman region code with our own native
JS implementation. Just tweak this interface to make it a tiny bit
easier for our own code to implement.