Modify mountd to handle the experimental nfs server as well as the

Modify mountd to handle the experimental nfs server as well as the
regular one. It now takes a "-4" command line argument to force it
to use the experimental server. Otherwise it will use the regular
server unless the experimental server is the only one linked into
the kernel. A third kind of line has been added to /etc/exports,
which is specific to NFSv4 and defines where the NFSv4 tree root is
and can be used to limit access to NFSv4 state handling operations
that do not use any file handle.

Approved by:	kib (mentor)