Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Remove end of line whitespace.

Add the possibility to specify a threshold for the number of negative cache
results required to have the cache return lookup failure.

A new configuration parameter is introduced, which must be set to a value
greater than 1 to activate this feature. The default behavior is unchanged.

The purpose of this change is to allow probes for the existence of an entry
(which are expected to fail), before that entry is added to one of the
queried databases, without the cache returning the stale information from
the probe query until that cache entry expires. If, for example, a new user
account is created after checking that the new account name is available,
the negative cache entry would prevent immediate access to the account.

For that example, the new configuration option

negative-confidence-threshold passwd 2

will require a second negative query result to consider the negative cache
entry for a passwd entry valid, but if the user account has been created
between the queries, then the positive query result from the second query
will be cached and returned.

mdoc: consistently spell our email addresses <foo@FreeBSD.org>

Reviewed by: ru

The default hash table size is 257 not 255. Reword the rest of the line
slightly while here.

PR: bin/121671
Submitted by: Artis Caune artis.caune gmail.com
Approved by: ed (mentor)

o Correct a database name: "group" not "groups".

PR: docs/129853
Submitted by: Denis Barov
MFC after: 1 week

Forced commit to note repocopy:

The files were copied in order to rename cached to nscd.

Approved by: re (kensmith), brooks (mentor)

- Renaming repocopied cached to nscd

Approved by: re (kensmith), brooks (mentor)

Revise markup.

o Silence mdoc(7) warnings: remove an empty line, add missed .El macro.
New sentence - new line.

Specify default values for positive-policy and negative-policy .

- Extend the nsswitch to support Services, Protocols and Rpc
databases.
- Make nsswitch support caching.

Submitted by: Michael Bushkov <bushman__at__rsu.ru>
Sponsored by: Google Summer of Code 2005