except an absence of the directory is not considered an error
and doesn't produce a warning).
Put /usr/local/lib/perl5/*/man under OPTIONAL_MANPATH.
- An order of directives in manpath.config is now irrelevant.
- Get rid of infinite loop when PATH is unset or NULL, and
MANDATORY_MANPATH directory doesn't exist.
- mdoc(9)ify manpage.
Reviewed by: des, markm, sheldonh
80e770cf63