Cleanup namespace of dos-w32.el.

Cleanup namespace of dos-w32.el.
* lisp/dos-w32.el (minibuffer-history-case-insensitive-variables)
(path-separator, null-device, buffer-file-coding-system)
(lpr-headers-switches): Check system-type before modifying them.
(find-buffer-file-type-coding-system): Mark obsolete.
(w32-find-file-not-found-set-buffer-file-coding-system): Rename from
find-file-not-found-set-buffer-file-coding-system.
(w32-untranslated-filesystem-list, w32-untranslated-canonical-name):
(w32-add-untranslated-filesystem, w32-remove-untranslated-filesystem)
(w32-direct-print-region-use-command-dot-com, w32-untranslated-file-p):
(w32-direct-print-region-helper, w32-direct-print-region-function)
(w32-direct-ps-print-region-function): Rename by adding a "w32-" prefix.
* lisp/startup.el (normal-top-level-add-subdirs-to-load-path):
* lisp/ps-print.el (ps-print-region-function):
* lisp/lpr.el (print-region-function): Use new name.

* lisp/simple.el (copy-region-as-kill): Fix call to region-extract-function.

* lisp/emacs-lisp/bytecomp.el (byte-defop-compiler): Add new `2-and' handler.
(byte-compile-and-folded): New function.
(=, <, >, <=, >=): Use it.