MFC r273849:

Add support for "timeo", "actimeo", "noac", and "proto" options
to mount_nfs(8).  They are implemented on Linux, OS X, and Solaris,
and thus can be expected to appear in automounter maps.

Sponsored by:	The FreeBSD Foundation
MFC r273851:

Note that the "timeout" nfs option is in tenths of a second.

Sponsored by:	The FreeBSD Foundation
MFC r273852:

Fix handling of "conn" mount_nfs(8) option.

Sponsored by:	The FreeBSD Foundation
MFC r273853:

Make it clear that ACL flags are NFSv4-only.

Sponsored by:	The FreeBSD Foundation
MFC r273854:

Update acl(3) to expand on NFSv4 ACL support.

Sponsored by:	The FreeBSD Foundation
MFC r273848:

Get rid of obsolete code in mount_nfs(8).

MFC r273861:

Remove two functions unused after r273848.  Would be nice if clang
or at least scan-build yelled about it.

Sponsored by:	The FreeBSD Foundation
MFC r273896:

Build mount_nfs(8) with WARNS=6.

Sponsored by:	The FreeBSD Foundation
MFC r274278:

Improve wording in ctl.conf(5).

Sponsored by:	The FreeBSD Foundation