Optimize tail recursive calls while byte compiling.

Optimize tail recursive calls while byte compiling.

* lisp/emacs-lisp/byte-opt.el (byte-optimize-stack-adjustment)
  (byte-optimize-conv-return-goto), (byte-optimize-copy-ops),
  (byte-optimize-called-function), (byte-optimize-lapcode-tail-recursion):
  New functions.

* lisp/emacs-lisp/bytecomp.el: Add variables b-c-current-{defun,
  arglist}.
  (byte-compile-file-form-defmumble), (byte-compile): Set them.
  (byte-compile-out-toplevel): Use byte-optimize-lapcode-tail-recursion.