Closes #101: don't use new Emacs 24.4's colon load-path in Makefile

* Makefile (LOAD_PATH): Closes #101: Don't use new : (colon)
feature of upcoming Emacs 24.4.
Upgrade to cl-lib 0.4 and remove some compilation warnings.

* slime.el: Prefix all cl-functions with "cl-".

* contrib/slime-repl.el: Prefix all cl-functions with "cl-"

* lib/cl-lib.el: Upgrade bundled version to 0.4.