Add straightforward HiddenWS to WSType
Add straightforward HiddenWS to WSType

With NonEmptyWS and HiddenNonEmptyWS present, HiddenWS is obviously missing.

darcs-hash:20081006210548-23c07-4ddc29497068f5f4e4819960c0e1bd97bfd74812

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