i386/kvm: Hyper-v crash msrs set/get'ers and migration

KVM Hyper-V based guests can notify hypervisor about
occurred guest crash by writing into Hyper-V crash MSR's.
This patch does handling and migration of HV_X64_MSR_CRASH_P0-P4,
HV_X64_MSR_CRASH_CTL msrs. User can enable these MSR's by
'hv-crash' option.

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: <1435924905-8926-13-git-send-email-den@openvz.org>
[Folks, stop abrviating variable names!!! Also fix compilation on
 non-Linux/x86. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
