[xen] Add Opt.{map,join,default}
[xen] Add Opt.{map,join,default}

cheng--zhang/xenopsd,johnelse/xenopsd,koushikcgit/xenopsd,johnelse/xenopsd,koushikcgit/xenopsd,thomassa/xenopsd,djs55/xenopsd-previous,euanh/xenopsd,euanh/xenopsd,djs55/xenopsd-previous,simonjbeaumont/xenopsd,thomassa/xenopsd,djs55/xenopsd,djs55/xenopsd,simonjbeaumont/xenopsd,euanh/xenopsd,thomassa/xenopsd,koushikcgit/xenopsd,djs55/xenopsd,simonjbeaumont/xenopsd,cheng--zhang/xenopsd,cheng--zhang/xenopsd,djs55/xenopsd-previous,johnelse/xenopsd