Instead of creating just two materials (one for texturing and one for
solid primitives) the pango renderer now maintains a cache of
pipelines. The display list can request a pipeline for a texture from
the cache. The same pipeline cache is used by all display lists so
that the pipelines can be shared. This avoids changing the texture on
the material during a paint run.
Instead of using the CoglHandle type for material variables this updates
the pango code to use CoglMaterial * instead. CoglHandle is the old
typename which is being phased out of the API.