Added TODO note in mouse handling code

src/sdl2/mouse.rs

@@ -102,6 +102,7 @@ impl Cursor {
         }
     }
 
+    // TODO: figure out how to pass Surface in here correctly
     pub fn from_surface(surface: &surface::Surface, hot_x: int, hot_y: int) -> Result<Cursor, ~str> {
         unsafe {
             let raw = ll::SDL_CreateColorCursor(surface.raw, hot_x as i32,