Rewrite the cconv conversion algorithm, for clarity.

Rewrite the cconv conversion algorithm, for clarity.
* lisp/emacs-lisp/byte-opt.el (byte-compile-inline-expand): Adjust check for
new byte-code representation.
* lisp/emacs-lisp/cconv.el (cconv--convert-function): Rename from
cconv-closure-convert-function.
(cconv-convert): Rename from cconv-closure-convert-rec.
(cconv--analyse-use): Rename from cconv-analyse-use.
(cconv--analyse-function): Rename from cconv-analyse-function.
(cconv--analyse-use): Change some patterns to silence compiler.
(cconv-convert, cconv--convert-function): Rewrite.
* test/automated/lexbind-tests.el: New file.