* configure.ac: Check for 'emacs', substitute 'EMACS', and emit
'etc/indent-package.el'.
* etc/indent-package.el.in: New file.
* doc/contributing.texi (Formatting Code): Mention
'etc/indent-package.el'.
(Submitting Patches): Likewise, and link to the above node.
Co-authored-by: Alex Kost <alezost@gmail.com>
