Support 3D rendering to scaled primary surface.

git-svn-id: https://www.williamfeely.info/svn/dxgl@528 8a90861a-4eca-46d5-b744-240ff16d0c4d
Use 4x4 matrix for dithering; improves performance.
Downgrade GLSL fragment shaders with dithering to @version 110

git-svn-id: https://www.williamfeely.info/svn/dxgl@529 8a90861a-4eca-46d5-b744-240ff16d0c4d