Devices/Misc/VirtualKD: mistake in contributor name, apologies.

Devices/Misc/VirtualKD: new, slightly modified interface definition which avoids the need to know the rpc command header size

Devices/Misc/VirtualKD: fix code breakage due to padding

Devices/Misc: new VirtualKD stub/loader device, contributed by Ivan Shcherbakov (and heavily modified afterwards to integrate cleanly into VirtualBox and match the coding style)