gallivm: do texture swizzle after shadow compare

We need to swizzle after the shadow comparison so that the GL_DEPTH_MODE
functionality is handled properly.

This fixes all the piglit glsl-fs-shadow2d*.shader_test cases, except
for glsl-fs-shadow2dproj-bias.shader_test which fails because of a
bug in the GLSL compiler (fd.o 32395).
2 files changed