[Xmonad] [patch] size hints

This patch makes xmonad obey (some) size hints set by clients, for example the aspect ratio hint set by mplayer. I also implemented the max size and size increment hints, as some clients seem to get confused if their window is "too large" (for example Xephyr). Problems with this patch: - The hints are retrieved every wm operation, which could hurt over a slow link. They should be cached (and xmonad should listen to property events) - The code is not integrated in the layout algorithm, which results in ugly gaps between windows. - Too many lines of code.