This renames the global ctx and fb variables to test_ctx and test_fb
respectively in line with the names use on the master branch. This is to
make it easier to cherry pick patches from master.
This adds a simple test which sets an alpha test on a pipeline and
then renders a texture. It then verifies that the transparent parts of
the texture aren't drawn. This is currently failing with the GL3
driver because GL3 requires the alpha test to be implemented in GLSL
but the generated alpha test uniform is only updated for the GLES2
driver.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 4ec04507bfaf2d61707dccfb59ac7326962ee741)
