Log Message:
mail/mailutils: update to version 3.18

# Noteworthy changes in this release:

* New debugging shortcut: all

Using "all" in mailutils debug level specification enables all debugging
categories.  Syntactically, "all" can be used wherever an actual category
name is allowed, thus, e.g., "all.!=prot" enables all levels except
"prot" in all debugging categories.

* mail: fix and document interaction between mailutils configuration
files and mail command files.

* Bugfixes

** Minor fix in handling the EHLO command in smtp client.
** Improve docs.
** Minor fix in mhn and related tests.
** mail utility: use the "mailer" configuration capability.