Update tests to follow new syntax.

tests/reference_test.aer

@@ -1,10 +1,10 @@
 class Program {
 
-	function add_by_ref(int &$val) {
+	void add_by_ref(int &$val) {
 		$val += 7;
 	}
 
-	function main() {
+	void main() {
 		int $num = 7;
 		$this->add_by_ref($num);
 		var_dump($num);