~/.xmonad: volume & quodlibet shortcuts.

There's a bug when the master volume is off. Somehow the mute button
doesn't work then which is a little weird. Ideally I'd have the mute
button "pick up" the master volume state and then light up if it is
muted "externally", but it's a bit out of scope for now.

.xmonad/xmonad.hs

import XMonad.Layout.Fullscreen (fullscreenEventHook, fullscreenManageHook)
import XMonad.Util.Run (spawnPipe)
import XMonad.Util.EZConfig (additionalKeys)
import Graphics.X11.ExtraTypes.XF86
import System.IO (hPutStrLn)
import Data.IORef.MonadIO (newIORef, readIORef, modifyIORef)
import Control.Monad (when)
import Data.Monoid (All (All))
import qualified XMonad.StackSet as W
        ((mod4Mask, xK_b), spawnHere "chromium --allow-file-access-from-files"),
        ((mod4Mask .|. shiftMask, xK_b), spawnHere "chromium --incognito --allow-file-access-from-files"),
        ((0, xF86XK_AudioMute), spawn "amixer set Master toggle"),
        ((0, xF86XK_AudioLowerVolume), spawn "amixer set Master 5%-"),
        ((0, xF86XK_AudioRaiseVolume), spawn "amixer set Master 5%+"),
        ((mod4Mask .|. shiftMask, xK_m), spawnHere "quodlibet"),
        ((mod4Mask .|. shiftMask, xK_Tab), changeKbMap kbMap),
        ((mod4Mask .|. shiftMask, xK_l), spawn "slock"),