support arbitrary parens around formal parameters

dtool/src/cppparser/cppBison.yxx

@@ -1420,6 +1420,11 @@ formal_parameter_identifier:
   $$ = $2;
   $$->add_modifier(IIT_paren);
   $$->add_func_modifier($5, $7);
+}
+        | '(' formal_parameter_identifier ')'
+{
+  $$ = $2;
+  $$->add_modifier(IIT_paren);
 }
         ;