[xmonad] Adding handleEventHook to darcs man/xmonad.hs

[Wirt Wolff]

Excerpts from Spencer Janssen's message of Thu Mar 19 02:13:40 -0600 2009:
> 
> This seems to be cyclical.  A better definition for myEventHook:
> 
>     myEventHook = mempty
> 

Ugh, indeed. Thanks for catching and fixing that. Apparently my mental
state during patch creation was also 'mempty'!

Wiki darcs template file updated with mempty.

(Turns out mempty was not in scope, so patch sent to import Data.Monoid
for man/xmonad.hs, too.) Added a few other updates to doc to make patch
generation a little more worthwhile: 

* Updated ToggleStruts binding for mod-b, and left commented since
xmonad-contrib may not be installed,

* Used 'modm' instead of 'modMask' in bindings, since that shadowing
can be confusing during irc troubleshooting.

Apologies for not testing and resolving all this in original patch.

-- 
wmw