The -machine docs did not explain what the versioned machine
types are for, nor that they'll be maintained across
releases.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <20170725141041.1195-1-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>