glsl: Add a pass to propagate the "invariant" and "precise" qualifiers

Reviewed-by: Francisco Jerez <currojerez@riseup.net>

src/compiler/glsl/glsl_parser_extras.cpp

@@ -1885,6 +1885,7 @@ do_common_optimization(exec_list *ir, bool linked,
       OPT(do_dead_functions, ir);
       OPT(do_structure_splitting, ir);
    }
+   propagate_invariance(ir);
    OPT(do_if_simplification, ir);
    OPT(opt_flatten_nested_if_blocks, ir);
    OPT(opt_conditional_discard, ir);