Add more special scancodes

While working on Solaris automated installation, @ccope found that Packer was missing some scancodes needed to walk-through/get-out of the GUI to a command line shell. The `virtualbox` types were ported from the old veewee code whereas the `qemu` and `vmware` came from the newly added comment.

There are certainly more keys which could be added, but this was all that we needed for now.