GabbleFileTransferChannel: stub out Unix socket support unless GIBBER_TYPE_UNIX_TRANSPORT was built
GabbleFileTransferChannel: stub out Unix socket support unless GIBBER_TYPE_UNIX_TRANSPORT was built

mlundblad/telepathy-gabble,jku/telepathy-gabble,mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,jku/telepathy-gabble