Users should move to the new geom_vinum implementation instead.
The refcount logic which is being added to devices to enable safe module
unloading and the buf/vm work also in progress would require a major rework
of the (old)-vinum code to comply with the new semantics.
The actual source files will not be removed until I have coordinated with
the geomvinum people if they need any bits repo-copied etc.
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