Draw Operation merging

Merge simple bitmap draw operations and text operations to avoid
issuing individual gl draws for each operation. Merging other ops to
be done eventually.

The methods are different - the bitmap merging generates a single
mesh for reused, unclipped images (esp. repeated images in a listview)

The text approach queries just defers the normal font rendering until
the last drawText in the sequence that can share the same shader.

Patches are sorted and merged, but don't yet have a multiDraw
implementation. For now, the pretending-to-merge gives better sorting
behavior by keeping similar patches together.

Change-Id: Ic300cdab0a53814cf7b09c58bf54b1bf0f58ccd6