AppVeyor: use x64 environment
AppVeyor: use x64 environment

nismod/smif,willu47/smif,tomalrussell/smif,willu47/smif,tomalrussell/smif,willu47/smif,nismod/smif,nismod/smif,tomalrussell/smif,tomalrussell/smif,nismod/smif,willu47/smif