st/glsl_to_tgsi: explicitly track all input and output declaration

st/glsl_to_tgsi: explicitly track all input and output declaration

In order to be able to emit overlapping input and output array
declarations, we flip the logic of emitting those declarations on its
head: rather than iterating over slots and emitting the corresponding
declarations, we iterate over the declarations from GLSL and emit those.

v2: fix some regressions related to structs
v3: fix a regression in geometry and tessellation shader array handling

Acked-by: Edward O'Callaghan <funfunctor@folklore1984.net> (v2)
Reviewed-by: Dave Airlie <airlied@redhat.com> (v2)