[Xmonad] darcs patch: eliminate a few Eq a constraints in Stac... (and 4 more)

This is an amend-recorded patch fixing a conflict with sjanssen's improvement of the Layout instance. David Thu Sep 20 17:01:43 EDT 2007 David Roundy * eliminate a few Eq a constraints in StackSet. Thu Sep 20 17:05:27 EDT 2007 David Roundy * remove unneeded Ord constraint. Thu Sep 20 17:28:43 EDT 2007 David Roundy * add (unused) Layout to StackSet. Thu Sep 20 18:12:48 EDT 2007 David Roundy * move Layout into StackSet. WARNING! This changes the format of StackSet, and will definitely mess up your xmonad state, requiring at minimum a restart! Fri Sep 21 16:43:16 EDT 2007 David Roundy * make layouts preserved over restart