Disable KVM support if the kernel modules have broken memory slot handling

Disable KVM support if the kernel modules have broken memory slot handling

Prior to kvm-80, memory slot deletion was broken in the KVM kernel
modules.  In kvm-81, a new capability is introduced to signify that this
problem has been fixed.

Since we rely on being able to delete memory slots, refuse to work with
any kernel module that does not have this capability present.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5960 c046a42c-6fe2-441c-8c8c-71466251a162