SpawnOn: delete seen pids
SpawnOn: delete seen pids

Ignore-this: 8b15a60bba1edf1bab5fb77ac54eb12f

darcs-hash:20090213013011-25a6b-279244c622ea2066d94725e40434b81c4cdec1c0

yzhou61/xmonad-contrib,yzhou61/xmonad-contrib,yzhou61/xmonad-contrib