glsl: Simplify symbol table version checking.

glsl: Simplify symbol table version checking.

Previously, we stored the GLSL language version in the
glsl_symbol_table struct.  But this was unnecessary--all
glsl_symbol_table needs to know is whether functions and variables
have separate namespaces (they do in GLSL 1.10 only).

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Acked-by: Carl Worth <cworth@cworth.org>