Add the basic IPMI types and infrastructure to QEMU.  Low-level
interfaces and simulation interfaces will register with this; it's
kind of the go-between to tie them together.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>