shiny/driver/gldriver: respect the draw transform.

Prior to this change, all textures were drawn 1:1 axis-aligned starting
at the top-left corner, regardless of the arguments to Draw.

Change-Id: I3d0cf025eb556f9a3cde56f5cda06415dbb12503
Reviewed-on: https://go-review.googlesource.com/14812
Reviewed-by: David Crawshaw <crawshaw@golang.org>
4 files changed