Trimm out now unused option LK_EXCLUPGRADE from the lockmgr namespace.
This option just adds complexity and the new implementation no longer
will support it, so axing it now that it is unused is probabilly the
better idea.

FreeBSD version is bumped in order to reflect the KPI breakage introduced
by this patch.

In the ports tree, kris found that only old OSKit code uses it, but as
it is thought to work only on 2.x kernels serie, version bumping will
solve any problem.