glsl: add uniform and program resource support (v2)

glsl: add uniform and program resource support (v2)

This adds linker support for subroutine uniforms, they
have some subtle differences from real uniforms, we also hide
them and they are given internal uniform names.

This also adds the subroutine locations and subroutine uniforms
to the program resource tracking for later use.

v1.1: drop is_subroutine_def

v2: handle explicit location properly, ARB_explicit_location
has a lot of language for subroutine shaders.
Calculate a link time the number of compatible subroutines
for a uniform, to make program resource easier later.

Acked-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>