proper file attribute (a.k.a. "resource fork") is picked up when
the filehandle is mapped back to filesystem object.
This should make attributes working on NFS-exported NTFS filesystems
or other layered filesystems using filehandles.
ntnode->ntmp->ntm_* values
ntfs_inactivate(): as NTFS doesn't support any filesystem changes,
it's not needed to check whether the file handle is stale;
the check was bogus anyway - besides the value of vp->v_usecount
was checked with unlocked vnode, the vnode was unnecessarily
_always_ recycled when the filesystem containing it has been
mounted with mask (-i parameter to mount_ntfs(1))
not specified or 0 -- unbelievable, but true
ntfs_reclaim(): don't call VOP_UNLOCK() even on FreeBSD - it's not
done for any other their filesystem, so it should not be done even
for NTFS
ntfs_access(): remove the commented-out check for immutable flag, it doesn't
make sense for NTFS
other miscelaneous cosmetic cleanups
guard the setting and checking of i_usecount by simplelock; as
situation where there would be several users of same ntnode is
extremery rare, it's not worth the efford to change the code to
hold the (exclusive) lock only when it's needed
* in struct fnode, g/c f_dev & f_type (former is already in ntnode,
latter is in parent vnode), move f_devvp from struct fnode into
struct ntnode (no reason this should be copied in each fnode)
* f_lock is only needed for FreeBSD (for their totally disgusting
and insane way of doing generic vnode locking)
* g/c f_mp, it was write-only
* some comments added
