Re: un-deprecating CL

[Richard Stallman]

    > These changes are ok to install, as long as you update the Emacs Lisp
    > manual while you're at it.  As natural extensions, they don't cost
    > much in terms of increasing the complexity of Emacs Lisp.

    On the other hand, they may come at a performance cost and have very
    little use.

Comparison are open-coded by the compiler, so this will require a compiler
change but won't cause any performance penalty.

As for mapcar, it is pretty slow already, and the main cost is in
calling the user's function.  That won't get any slower.