Mouse support (redux)

[redchair123]

So I hacked something together, but I figured you could do it better :)

mousemask(ALL_MOUSE_EVENTS, NULL);

I put that in the panel init but that's not the right place for the call. This is sufficient to just respond to a mouse event (so that you could receive the nc.keys.MOUSE event)

To actually get the mouse, you need to call getmouse and expose the struct via the node interface.

What I ended up doing was creating a separate callback inputMouse. I don't think that's the right approach but at least it works :)