glsl: Pass _mesa_glsl_parse_state into matching_signature and such.

During compilation, we'll use this to determine built-in availability.
The plan is to have a single shader containing every built-in in every
version of the language, but filter out the ones that aren't actually
available to the shader being compiled.

At link time, we don't actually need this filtering capability: we've
already imported prototypes for every built-in that the shader actually
calls, and they're flagged as is_builtin().  The linker doesn't import
any additional prototypes, so it won't pull in any unavailable
built-ins.  When resolving prototypes to function definitions, the
linker ensures the values of is_builtin() match, which means that a
shader can't trick the linker into importing the body of an unavailable
built-in by defining a suspiciously similar prototype.

In other words, during linking, we can just pass in NULL.  It will work
out fine.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>

src/glsl/ir_function.cpp

@@ -116,14 +116,16 @@ parameter_lists_match(const exec_list *list_a, const exec_list *list_b)
 
 
 ir_function_signature *
-ir_function::matching_signature(const exec_list *actual_parameters)
+ir_function::matching_signature(_mesa_glsl_parse_state *state,
+                                const exec_list *actual_parameters)
 {
    bool is_exact;
-   return matching_signature(actual_parameters, &is_exact);
+   return matching_signature(state, actual_parameters, &is_exact);
 }
 
 ir_function_signature *
-ir_function::matching_signature(const exec_list *actual_parameters,
+ir_function::matching_signature(_mesa_glsl_parse_state *state,
+                                const exec_list *actual_parameters,
 			        bool *is_exact)
 {
    ir_function_signature *match = NULL;
@@ -203,7 +205,8 @@ parameter_lists_match_exact(const exec_list *list_a, const exec_list *list_b)
 }
 
 ir_function_signature *
-ir_function::exact_matching_signature(const exec_list *actual_parameters)
+ir_function::exact_matching_signature(_mesa_glsl_parse_state *state,
+                                      const exec_list *actual_parameters)
 {
    foreach_iter(exec_list_iterator, iter, signatures) {
       ir_function_signature *const sig =