vmm/virtualbox: Silence unrecognized-version warning on VBox 2.1.2
vmm/virtualbox: Silence unrecognized-version warning on VBox 2.1.2

- VirtualBox 2.1.2 changes the settings version for reasons that do
not affect us at all (see VirtualBox OSE commit r15708).  Add the new
settings version to the list of supported versions to silence the
"unknown version" warning.

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr