core: Use namespaces from all entries in a feed
core: Use namespaces from all entries in a feed

We were previously assuming that all entries in the feed had identical sets
of namespaces, and just using the namespaces from the first entry. This can
be untrue for batch feeds, so we must use the namespaces from all entries in
the feed.

Pecisk/libgdata-gtasks,Pecisk/libgdata,pwithnall/libgdata,pwithnall/libgdata,Distrotech/libgdata,GNOME/libgdata,Pecisk/libgdata-gtasks,Distrotech/libgdata,Distrotech/libgdata,Pecisk/libgdata-gtasks,Pecisk/libgdata,Pecisk/libgdata