fix interface test

vlib/v/tests/cstrings_test.v

@@ -1,5 +1,4 @@
-
-fn test_cstring(){
+fn test_cstring() {
 	w := c'world'
 	hlen := C.strlen(c'hello')
 	wlen := C.strlen(w)

vlib/v/tests/interface_test.v

@@ -22,6 +22,8 @@ fn (d Dog) name() string {
 	return 'Dog'
 }
 
+fn test_todo() {}
+
 /*
 interface Speaker {
 	name ()string