Clipboard history for StumpWM.

Implements a simple clipboard history (text only) manager by polling the clipboard selection periodically and keeping a stack of latest clippings.

** Usage
Add
#+BEGIN_SRC lisp
(load-module "clipboard-history")

(define-key *root-map* (kbd "C-y") "show-clipboard-history")
;; start the polling timer process
(clipboard-history:start-clipboard-manager)
#+END_SRC
