Keyboard layout switcher for StumpWM

** Usage
Add 
#+begin_src lisp
(load-module "kbd-layouts")
#+end_src
to =.stumpwmrc= 

You can specify your keyboard layouts using the function
=KEYBOARD-LAYOUT-LIST=. Layouts are represented by strings identical to
those used by setxkbmap, e.g.:
#+begin_src lisp
(keyboard-layout-list "us" "pl" "ru -variant phonetic")
#+end_src
You can also specify the behavior of the CapsLock key using
variable =*CAPS-LOCK-BEHAVIOR*=. Available are the following values:
- =:normal= - CapsLock serves as CapsLock
- =:ctrl= - CapsLock serves as additional Ctrl
- =:swapped= - CapsLock and Ctrl are swapped
By default the command =SWITCH-KEYBOARD-LAYOUT= is bound to the key
combination =s-SPC= (=WinKey-Space=).

