glsl/types: add new subroutine type (v3.2)

glsl/types: add new subroutine type (v3.2)

This type will be used to store the name of subroutine types

as in subroutine void myfunc(void);
will store myfunc into a subroutine type.

This is required to the parser can identify a subroutine
type in a uniform decleration as a valid type, and also for
looking up the type later.

Also add contains_subroutine method.

v2: handle subroutine to int comparisons, needed
for lowering pass.
v3: do subroutine to int with it's own IR
operation to avoid hacking on asserts (Kayden)
v3.1: fix warnings in this patch, fix nir,
fix tgsi
v3.2: fixup tests

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>
Signed-off-by: Dave Airlie <airlied@redhat.com>
tests: fix warnings