Unfortunately, whilst the cursors video plays fine in standard video
players, the ScummVM AVIDecoder can't seem to handle it. So for now
I've left the decode in place but commented out, and I'm setting up
a dummy cursor
Turns out that some of the messages have properties that the objects
that handle them can set. For example, the CMouseDragStartMsg has a
_dragItem property that an item that allows dragging will explicitly
set, allowing the input handler to keep track of what was dragged.