Changed weak-memory mode in CBLCache to avoid crashes
Changed weak-memory mode in CBLCache to avoid crashes

For some reason the "ZeroingWeakMemory" option doesn't work; it might
only support GC, not ARC. Switched to "WeakMemory", which does work.

brendand/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,macoscope/couchbase-lite-ios,amco/couchbase-lite-ios,ryuzmukhametov/couchbase-lite-ios,amco/couchbase-lite-ios,macoscope/couchbase-lite-ios,ryuzmukhametov/couchbase-lite-ios,jkingyens/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,couchbase/couchbase-lite-ios,pegli/couchbase-lite-ios,jkingyens/couchbase-lite-ios,lordkev/couchbase-lite-ios,mz2/couchbase-lite-ios,amco/couchbase-lite-ios,jkingyens/couchbase-lite-ios,tomco/couchbase-lite-ios,amco/couchbase-lite-ios,evsukov89/couchbase-lite-ios,mz2/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,tomco/couchbase-lite-ios,alfared/couchbase-lite-ios,lordkev/couchbase-lite-ios,pegli/couchbase-lite-ios,pegli/couchbase-lite-ios,couchbase/couchbase-lite-ios,ryuzmukhametov/couchbase-lite-ios,jkingyens/couchbase-lite-ios,ryuzmukhametov/couchbase-lite-ios,evsukov89/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,amco/couchbase-lite-ios,tomco/couchbase-lite-ios,pegli/couchbase-lite-ios,Chavenay/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,macoscope/couchbase-lite-ios,alfared/couchbase-lite-ios,evsukov89/couchbase-lite-ios,myDario/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,Chavenay/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,Chavenay/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,alfared/couchbase-lite-ios,brendand/couchbase-lite-ios,myDario/couchbase-lite-ios,brendand/couchbase-lite-ios,myDario/couchbase-lite-ios,brendand/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,macoscope/couchbase-lite-ios,brendand/couchbase-lite-ios,amco/couchbase-lite-ios,tomco/couchbase-lite-ios,amco/couchbase-lite-ios,alfared/couchbase-lite-ios,couchbase/couchbase-lite-ios,mz2/couchbase-lite-ios,lordkev/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,lordkev/couchbase-lite-ios,couchbase/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios