I'd like to be able to easily choose between several lisp implementations
when starting slime (sbcl, cmucl, clisp). The most recent message I was able
to find, on http://article.gmane.org/gmane.lisp.slime.devel/3932
suggested using slime-register-lisp-implementation, but I see that this
function has been deleted. What's the current 'right' way to do this?