MFC: r214048, r214053

MFC: r214048, r214053
Modify the NFS clients and the NLM so that the NLM can be used
by both clients. Since the NLM uses various fields of the
nfsmount structure, those fields were extracted and put in a
separate nfs_mountcommon structure stored in sys/nfs/nfs_mountcommon.h.
This structure also has a function pointer for a function that
extracts the required information from the mount point and nfs vnode
for that particular client. Also, fix the type of the 3rd argument for
this function.

git-svn-id: svn://svn.freebsd.org/base/stable/8@214612 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f