MFC: r345995
Delete the BUGS entry related to failing when jails are enabled.

r345994 has finally fixed the bug that caused the nfsuserd(8) daemon to
fail when jails were enabled, so delete the BUGS entry from the man page.

MFC: r320659
Add a Bugs section that indicates that the nfsuserd doesn't work
when jails are being used on the system.
It is hoped that the patches in PR#205193 will someday get tested/debugged
so that they can be MFC'd to fix this.

This is a content change.

MFC: r317270
Get rid of bogus statement in the nfsuserd.8 man page.

The nfsuserd.8 man page stated that a usertimeout of 0 would disable
the cache timeout. This was simply not true, so this patch deletes
the sentence.

This is a content change.

MFC: r291535
Document the new "-manage-gids" option for the nfsuserd daemon.
This is a content change.

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

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

Fix typos and spelling mistakes.

Add two new utilities and two new daemons to /usr/src/usr.sbin that
are specifically used by the experimental nfsv4 subsystem.
nfscbd - The NFSv4 client callback daemon.
nfsuserd - The NFSv4 daemon that maps between user and group name
and their corresponding uid/gid numbers.
nfsdumpstate - A utility that dumps out the NFSv4 Open/Lock state.
nfsrevoke - Administratively revokes an NFSv4 client, releasing all
NFSv4 Open/Lock state it holds on the server.

Approved by: kib (mentor)