Re: more ALTER .. DEPENDS ON EXTENSION fixes

Thanks for the reviews; I pushed 0001 now, again to all branches since
9.6.  Because of the previous commit, the fact that multiple statements
are emitted is not important anymore: the server will only restore the
first one, and silently ignore subsequent ones.  And once you're using a
system in that state, naturally only one will be emitted by pg_dump in
all cases.

What remains on this CF item is the new feature to remove an existing
dependency.  As Tom says, given the little use this feature gets it
doesn't sound worth the destabilization risk in back branches, so I'm
going to push it only to master -- but not yet.

Thanks,

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services