glsl: Silence several "warning: unused parameter"

src/glsl/ir_function_detect_recursion.cpp

@@ -289,6 +289,8 @@ emit_errors_unlinked(const void *key, void *data, void *closure)
    function *f = (function *) data;
    YYLTYPE loc;
 
+   (void) key;
+
    char *proto = prototype_string(f->sig->return_type,
 				  f->sig->function_name(),
 				  &f->sig->parameters);
@@ -308,6 +310,8 @@ emit_errors_linked(const void *key, void *data, void *closure)
       (struct gl_shader_program *) closure;
    function *f = (function *) data;
 
+   (void) key;
+
    char *proto = prototype_string(f->sig->return_type,
 				  f->sig->function_name(),
 				  &f->sig->parameters);