Use a common implementation of the matrix stack for fixed-function OpenGL.

Change-Id: Ie51cddb3465f72375f20c704293d0850c95a735b
Reviewed-on: https://swiftshader-review.googlesource.com/2600
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>