Re-add opt_mac.h include, which is required in order for MNT_MULTILABEL to be set properly on devfs.  Otherwise, it isn't possible to set labels on /dev nodes.
Re-add opt_mac.h include, which is required in order for MNT_MULTILABEL
to be set properly on devfs.  Otherwise, it isn't possible to set labels
on /dev nodes.

Reported by:	Sergio Rodriguez <sergiorr at yahoo.com>
MFC after:	3 days

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase