* lisp/emacs-lisp/cl.el: New compatibility file.
* emacs-lisp/cl-lib.el, lisp/emacs-lisp/cl-seq.el, lisp/emacs-lisp/cl-macs.el:
* lisp/emacs-lisp/cl-extra.el: Rename all top-level functions and variables
to obey the "cl-" prefix.
* lisp/emacs-lisp/macroexp.el (macroexpand-all-1): Adjust to new name.
