mesa/sso: Implement _mesa_UseProgramStages

mesa/sso: Implement _mesa_UseProgramStages

Now arb_separate_shader_object-GetProgramPipelineiv should pass.

V3 (idr):
* Change spec references to core OpenGL versions instead of issues in
  the extension spec.
* Split out from previous uber patch.

v4 (idr): Use _mesa_has_geometry_shaders in _mesa_UseProgramStages to
detect availability of geometry shaders.

v5 (idr): Whitespace cleanup, use _mesa_lookup_shader_program_err
instead of open-coding it again, and update some comments at the end of
_mesa_UseProgramStages.  All suggested by Eric.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>