urxvt: throw VM_URGENT on a bell
zsh: try to save some typing
Delegate keyboard layout switching to XBindKeys

It used to be handled by XMonad, but that caused problems with
XScreenSaver: once the screen is locked, I couldn't switch layouts
anymore. That wasn't much of a problem if I locked the screen manually
using an XMonad hotkey--there, I just set the layout to the default
one--but when the screen was locked automatically (due to idle)
I couldn't get back in without killing XScreenSaver altogether.