#12 mouse_support assumes map starts at top of screen

[Ilmari Karonen]

When mouse_support is combined with align_message:top, mouse clicks are mapped to a position two squares below the character that was actually clicked. It looks as if the mouse_support code simply takes the mouse click coordinates on the screen and directly converts them to map coordinates, without first subtracting the offset from the top-left corner of the screen to that of the map.

(Tested on NAO.)