vmm/kvm: Add support for memory image save/restore
vmm/kvm: Add support for memory image save/restore

- Fork and exec KVM ourselves, rather than using the system() wrapper,
so that we can do things while it is running

- Add support for suspending when the user hits Enter at the original
xterm console

- Add support for resuming when a suspended memory image exists

- Have KVM connect its monitor console to a listening Unix domain socket
opened by the KVM driver, in order to support the above

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr