vmware: add legacy text-clipboard backdoor commands (6-9)
Host stages bytes via the vmware-clipboard-host bus event; guest polls
GETSELLENGTH/GETNEXTPIECE. Guest pushes via SETSELLENGTH/SETNEXTPIECE
and the device emits vmware-clipboard-guest when the buffer fills.
Same protocol as open-vm-tools' pre-RPC copy/paste, so a tiny Win9x
agent can do IN EAX,DX from ring 3 with no driver.