This needs some work on the window ordering and things like that, but it
works quite nicely as a starting point.
The keyboard shortcut is Logo+Tab. :^)
The algorithm I came up with is O(n^2) but given the small numbers of rects
we're typically working with, it doesn't really matter. May need to revisit
this in the future if we find ourselves with a huge number of rects.
This is a monster patch that required changing a whole bunch of things.
There are performance and stability issues all over the place, but it works.
Pretty cool, I have to admit :^)
