resend for bug fix related to removal of irqfd

Support an inter-vm shared memory device that maps a shared-memory object as a
PCI device in the guest.  This patch also supports interrupts between guest by
communicating over a unix domain socket.  This patch applies to the qemu-kvm
repository.

    -device ivshmem,size=<size in format accepted by -m>[,shm=<shm name>]

Interrupts are supported between multiple VMs by using a shared memory server
by using a chardev socket.

    -device ivshmem,size=<size in format accepted by -m>[,shm=<shm name>]
           [,chardev=<id>][,msi=on][,ioeventfd=on][,vectors=n][,role=peer|master]
    -chardev socket,path=<path>,id=<id>

The shared memory server, sample programs and init scripts are in a git repo here:

    www.gitorious.org/nahanni

Signed-off-by: Cam Macdonell <cam@cs.ualberta.ca>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit 6cbf4c8c)