two unrelated little fixes:
bottomwin:
	if bottom was used a few times, rio lost track of the window
	ordering, because w->topped was zero for several windows.
	setting it to a lower (negative) number each time fixes that.

deleting windows:
	a change so that if you point to a window to delete it,
	releasing the button off the window aborts the action.
	yes, it is possible to do this by chording with another
	button, but i feel this way is more intuitive and less easy
	to muck up (important when you might lose important info).
	BTW, i think the cursor when deleting a window should be distinguished,
	as it was in 8½ - i'll submit a patch to reinstitute the old bones
	cursor, if it's not considered a bad idea.