[xmonad] A patch for X.A.GroupNavigation to not rely on containers 0.3.0.0

Hi folks, I'm attaching a patch that implements the two problematic functions Seq.filter and Seq.breakl in X.A.GroupNavigation from scratch. So this should compile also on a vanilla ghc < 6.12. Since I only have ghc 6.12, I wasn't able to test whether this compiles with ghc < 6.12, only that the module still works. Cheers, Norbert