parser: check (mut f Foo) syntax

examples/vweb/vweb_example.v

@@ -17,27 +17,27 @@ fn main() {
 	vweb.run<App>(port)
 }
 
-pub fn (app mut App) init() {
+pub fn (mut app App) init() {
 	app.vweb.handle_static('.')
 }
 
-pub fn (app mut App) json_endpoint() {
+pub fn (mut app App) json_endpoint() {
 	app.vweb.json('{"a": 3}')
 }
 
-pub fn (app mut App) index() {
+pub fn (mut app App) index() {
 	app.cnt++
 	$vweb.html()
 }
 
-pub fn (app mut App) reset() {
+pub fn (mut app App) reset() {
 }
 
-pub fn (app mut App) text() {
+pub fn (mut app App) text() {
 	app.vweb.text('Hello world')
 }
 
-pub fn (app mut App) cookie() {
+pub fn (mut app App) cookie() {
 	app.vweb.set_cookie('cookie', 'test')
 	app.vweb.text('Headers: $app.vweb.headers')
 }