Virtio is now part of the FreeBSD base kernel
Remove call to freebsd-update
Fix package names
Building virtualbox-ose-additions requires /usr/src

So we'll just install from the binary.
Add wait before fetch command
Fix comment
Package of guest additions requires xorg-server - which is not available

As a binary package
Fetch and extract /usr/src and /usr/lib32 to build Vbox-OSE
Add yasm