Merge the NFSv4.1 server code in projects/nfsv4.1-server over
into head. The code is not believed to have any effect
on the semantics of non-NFSv4.1 server behaviour.
It is a rather large merge, but I am hoping that there will
not be any regressions for the NFS server.

MFC after:	1 month
 - Fix handling of "new" style of ioctl in compatiblity mode [1];
 - Reorganize code and reduce diff from upstream;
 - Improve forward compatibility shims for previous kernel;

Reported by:	sbruno [1]
X-MFC-With:	r268075
Document r268045, vt(4) now in GENERIC.
Remove r260888, VT kernel configuration file is gone.

Sponsored by:	The FreeBSD Foundation
Bump __FreeBSD_version since r268115 changed the internal
interfaces used between the NFS related modules, including
the krpc.