Fix prototypes, propagate const where applicable.

MUST make lo0 up before any IPv6 operations.
it will be considered a pilot error if you don't.
(I prefer to have lo0 initialized automatically)

includes some works from todd@ and millert@
verified by todd@ and millert@

Redefining it as a typedef is an error, as it prevents overloading
on e.g., int/wchar_t separately.

/usr/libexec/locate.updatedb does run as nobody the redirection is
done as root so the resulting file is owned by root.
sync log file owner/mode with what is is newsyslog.conf

Install it under /usr/include

(K&R-style type promotions are evil),

their own malloc() implementation.

didn't do so for us.  By default, malloc() zeros out the space it
allocates but the programmer cannot rely on this as it is implementation-
specific (and configurable via /etc/malloc.conf)

/usr/local/sbin/sshd instead, if it is there.

- avoid .Xref to one's own manpage

when it doesn't exist.