KVM kernel can send guest crash events into userspace.
Appropriate guest crash handler is called when kernel guest
crash event received. Guest crash event recognized by a
KVM_SYSTEM_EVENT_CRASH type of system event.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Andreas Färber <afaerber@suse.de>
Message-Id: <1435924905-8926-11-git-send-email-den@openvz.org>
[Rebase: add lock/unlock iothread around qemu_system_guest_panicked - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>