Heads up: default nfs client switched to new one

[Rick Macklem]

The commit r221124 switches the default NFS client to the new one in head.
The fstype "newnfs" is now "nfs" and the regular/old NFS client is
now fstype "oldnfs". As such, "mount -t nfs ..." will use the new client.

Although most kernels will still work with the old mount(8) and
mount_nfs(8) binaries (the exception is one built with "options NFSCL"
but not "options NFSCLIENT"), you should build fresh mount(8) and
mount_nfs(8) binaries.

To use the old NFS client...
You'll need new binaries for mount(8) and mount_nfs(8), plus a link
in /sbin to mount_nfs called mount_oldnfs.
Then you can use the old NFS client via:

mount -t oldnfs ...

Systems using a diskless root NFS fs will need to have the new client
linked into their kernels via "options NFSCL". Both "options NFSCL"
and "options NFSCLIENT" can be specified for the kernel. If you do
that, you can switch back to the old NFS client by changing the fstype
field of etc/fstab for the root fs on the NFS server to "oldnfs" plus adding a
line like:

vfs.root.mountfrom="oldnfs:"

to boot/loader.conf in the root fs on the server.

Hopefully, you won't need to do anything to keep things working
and this won't cause you grief, rick