Fix A.OnScreen example code typo
Fix A.OnScreen example code typo

Ignore-this: 486bfc9edc38913c8863e2d5581359eb

darcs-hash:20101212161850-1499c-2fb7b209db6b8bfb50635a59f0d0ea7ef02184f3

yzhou61/xmonad-contrib,yzhou61/xmonad-contrib,yzhou61/xmonad-contrib