[dev] [dwm] [patch] Fix for retarded clients that send unmapnotify events

Mathematica 7 and 8, probably plenty of other versions, and maybe even
some other retarded clients, send UnmapNotify events for their help
windows right after they get created. dwm then forgets about the window
and it's a huge pain in the ass to work with. Don't ask me why, I'm not
drunk and stoned enough to be able to think like Mathematica devs. But I
have a simple patch attached, which ignores all UnmapNotify events that
don't come from the server.

--Valentin