* lisp/emacs-lisp/bytecomp.el (byte-compile-force-lexical-warnings): New var.

* lisp/emacs-lisp/bytecomp.el (byte-compile-force-lexical-warnings): New var.
(byte-compile-preprocess): Use it.
(byte-compile-file-form-defalias): Try a bit harder to use macros we
can't quite recognize.
(byte-compile-add-to-list): Remove.
* lisp/emacs-lisp/cconv.el (cconv-warnings-only): New function.
(cconv-closure-convert): Add assertion.

* lisp/emacs-lisp/map-ynp.el: Use lexical-binding.
(map-y-or-n-p): Remove unused vars `tail' and `object'.
Factor out some repeated code.
* etc/NEWS (utf-8 for el): Move to the incompatible section.