Import ptexinfmt.el from Wanderlust.

Import ptexinfmt.el from Wanderlust.

* texi/Makefile.in (INFOSWI, XINFOSWI): Load ptexinfmt.el.

* lisp/dgnushack.el (dgnushack-texi-format): Don't require `texinfmt'.
(dgnushack-install-package): Don't install ptexinfmt.el.
(dgnushack-make-package): Don't include ptexinfmt.el in MANIFEST.
(dgnushack-compile): Don't compile dgnushack.el nor ptexinfmt.el.
(dgnushack-unexported-files, dgnushack-tool-files): New constants.

* lisp/Makefile.in (install-package): No need to remove dgnushack.elc.
(install): Don't install ptexinfmt.el; no need to remove dgnushack.elc.

* lisp/ptexinfmt.el: New file imported from Wanderlust.