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?