Add functions to allow cleaning up only screens which disappear. This
works better where killing the statusbar for a specific screen is
possible. The old way is still relevant for setups which do not have
such a method (e.g., safeSpawn xmobar/spawnPipe xmonadpropwrite).
Hooks.DynamicBars was previously using an MVar and the unsafePerformIO hack (
http://www.haskell.org/haskellwiki/Top_level_mutable_state ) to store bar
state. Since ExtensibleState exists to solve these sorts of problems, I've
switched the file over to use unsafePerformIO instead.
Some functions' types had to be changed to allow access to XState, but the
public API is unchanged.
XMonad core re-exports Control.Monad.State, which includes
a function "state" if you happen to use mtl-2. Since there's
a chance xmonad still works with mtl-1 avoid imports like:
import XMonad hiding (state)
