Fixed compile issue for non-ARC client apps
Fixed compile issue for non-ARC client apps

Somehow Clang didn't like the declaration of CBLReplication.authenticator
in a non-ARC compile. Added 'strong' attribute to it.

brendand/couchbase-lite-ios,pegli/couchbase-lite-ios,amco/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,alfared/couchbase-lite-ios,amco/couchbase-lite-ios,macoscope/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,tomco/couchbase-lite-ios,alfared/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,amco/couchbase-lite-ios,pegli/couchbase-lite-ios,brendand/couchbase-lite-ios,tomco/couchbase-lite-ios,Chavenay/couchbase-lite-ios,tomco/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,brendand/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,Chavenay/couchbase-lite-ios,amco/couchbase-lite-ios,lordkev/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,alfared/couchbase-lite-ios,tomco/couchbase-lite-ios,couchbase/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,Chavenay/couchbase-lite-ios,alfared/couchbase-lite-ios,macoscope/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,lordkev/couchbase-lite-ios,brendand/couchbase-lite-ios,couchbase/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,lordkev/couchbase-lite-ios,amco/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,macoscope/couchbase-lite-ios,lordkev/couchbase-lite-ios,amco/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,couchbase/couchbase-lite-ios,brendand/couchbase-lite-ios,pegli/couchbase-lite-ios,macoscope/couchbase-lite-ios,amco/couchbase-lite-ios,pegli/couchbase-lite-ios,couchbase/couchbase-lite-ios