Remove X.A.GroupNavigation.currentWindow
Remove X.A.GroupNavigation.currentWindow

Ignore-this: 4b202a9c9e3a13c5e34862784ea4acfa

This function does the same as X.StackSet.peek and all its uses have been
replaced with X.StackSet.peek.

darcs-hash:20110920083922-18a2b-617c85f913bacb3ad9239f0a6ee8afc1e4c28d41

jthornber/XMonadContrib,jthornber/XMonadContrib