Since we use IconicState as our hidden state, check for the hidden flag
and unmanage the client if we're not hidden (basically if NormalState)
during an UnmapNotify event.

Resolves an issue with mplayer going fullscreen while not using NetWM
hints; behaviour regression reported by Ido Admon.
Prepend the group shortcut in the client search menu; from Thomas Adam.
Likewise, prepend shortcut in unhide menu.
Always highlight the first menu item (helpful to see selected items when
not using a mouse and therefore not generating Expose/MotionNotify
events); from Thomas Adam.