VFS messaging/interfacing work stage 3/99: Bring in the journaling

VFS messaging/interfacing work stage 3/99:  Bring in the journaling
(and other) facilities infrastructure.  This is not yet operational and
will probably change, but is being brought in now to serve as a foil to
ensure that the namespace and range locking work is properly integrated with
the intended journaling and cache coherency infrastructure.

This commit also reserves some space in the vop_ops args structures to
reduce pain later on.

Since no flags are yet set in vop_ops this commit should not result in
any operational changes.