Provide means to find original window by its decoration.
Provide means to find original window by its decoration.

Ignore-this: fad8cb7fb4c2785b14b97d48f19604cc

In order to enable user to write custom `decorationMouseFocusHook' and
`decorationMouseDragHook' hooks we need to provide him with means to
lookup original window by its decoration.

Module Decoration has internal function `lookFor' for exactly the same
purpose. I exported it under a slightly different name and without
exposing internals of DecorationState.

darcs-hash:20090621194652-5701e-3fe157f99b1ea31377b0d77db4fd3a0314b553fd

kmels/xmonad-launcher,kmels/xmonad-launcher