This goes on top of MR 320 and 345.
-- v4: tests/shader-runner: Add a '--dump-dxil' command line switch. tests/shader-runner: Test shaders with dxcompiler. tests/shader-runner: Replace immediate shader type strings with an enum. tests/shader-runner: Do not exit if a 'require' directive is not met. tests/shader-runner: Handle individual keywords in shader directives.