mesa/st: glsl_to_tgsi: add register rename mapping evaluator

mesa/st: glsl_to_tgsi: add register rename mapping evaluator

The remapping evaluator first sorts the temporary registers ascending
based on their first life time instruction, and then uses a binary search
to find merge canidates.
For the initial sorting it uses std::sort because qsort is quite slow in
comparison. By removing the define USE_STL_SORT in
  src/mesa/state_tracker/st_glsl_to_tgsi_temprename.cpp
one can enable the alternative code path that uses qsort.

Registers that are not written to are not considered for renaming since in
glsl_to_tgsi_visitor::renumber_registers they are eliminated anyway.

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>