Remove workaround for ancient HTML generation code.

Add missing .El. From Henning Petersen in PR 49227.

Use more markup.

Document exponential backoff behavior and SIGHUP support, plus a couple
other minor edits.

branches: 1.18.6; 1.18.22; 1.18.26; 1.18.38;
Convert TNF licenses to new 2 clause variant

branches: 1.17.18;
Improve diagnostics section. Inspired by PR 32217 from Jeff Ito.

Sort SEE ALSO (first section, then name); new sentence, new line; bump date for previous.

YP -> NIS

Generate <>& symbolically. I'm avoiding .../dist/... directories for now.

Improve markup in once place, sort SEE ALSO, use standard headers.

Whitespace nits.

note that messages are send to syslog daemon using facility LOG_DAEMON.

* -insecure is for binding to insecure *servers*, not insecure *clients*.
noted by Bill Studenmund <skippy@macro.stanford.edu>.
* use .Tn YP instead of YP

branches: 1.9.2;
clarify that "domainname" in various pathnames is the actual domain name

use WARNS?=1 not WARNS=1 , cleanup manpage typo

Fix files using old TNF copyright notice

* use _yp_invalid_domain() (from libc) to validate the domainnames
* cleanup for -Wall
* use __RCSID

the following were inspired by openbsd:
* only allow connections from reserved ports
* implement -insecure, which turns off the above restriction (required
for sunos 3.x and ultrix)
* prevent more than 100 domains from being bound at once, preventing
a denial of service attacks

Change name of ypservers file to /var/yp/binding/domain.ypservers.
This is a compromise between the Solaris 2.5 naming of this file
(/var/yp/binding/domain/ypservers and /var/yp/binding/domain/vers)
and traditional NetBSD naming (/var/yp/binding/domain.vers).
Changing to the Solaris naming makes the C library incompatible
with ypbind. While it's easy to change the C library, I don't feel
right about introducing a gratuitous incompatibility.

The current name (/var/yp/domain/ypservers) conflicts with the name
of the YP map listing slave servers for a domain.

Per discussion w/ Chris Demetriou and Luke Mewburn.

.ypservers -> ypservers, to match Solaris 2.5

Add Luke Mewburn's support for a .ypservers file, which contains a list
of YP servers a client should bind to, mostly verbatim, but slightly
modified for better semantics when nagging servers if a ypset has been
issued. Default to broadcast mode if no .ypservers file is present.

Documentation changes to match, slightly tweaked by Scott Reynolds and
myself.

Closes PR #1759.

Copyright assigned to The NetBSD Foundation.

man page from Jason Thorpe