[xmonad] darcs patch: Module for automatic placement of floating windows

After months of getting all my floating windows spawned in the top-left corner and moving them by hand I finally broke down and wrote a floating window module. This module provides both a ManageHook and an X action to manually trigger repositioning of the focused window, supports both WindowArranger and "real" floating windows, and implements the usual placement policies (smart, fixed position, under the mouse). I haven't tested it extensively yet but everything I've tried to do with it worked as intended. At any rate, comments are welcome if you think there's something wrong with it. Hope someone finds this useful! Quentin