This patch adds field with content of KERNEL_GS_BASE MSR to QEMU note in
ELF dump.

On Windows, if all vCPUs are running usermode tasks at the time the dump is
created, this can be helpful in the discovery of guest system structures
during conversion ELF dump to MEMORY.DMP dump.

Signed-off-by: Viktor Prutyanov <viktor.prutyanov@virtuozzo.com>
Message-Id: <20180714123000.11326-1-viktor.prutyanov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>