Re: ALTER EXTENSION .. ADD/DROP weirdness

I wrote:
> Hmm.  I'm afraid that's going to break something, because I had had it
> like that originally and changed it in commit
> 988cccc620dd8c16d77f88ede167b22056176324.  However, I'm not quite sure
> *what* it will break, because it seems like in general extension
> dependencies ought to act pretty nearly like owner dependencies.
> In a quick look, this seems to be the only place where we're doing it
> differently (without a clear reason) for recordDependencyOnOwner and
> recordDependencyOnCurrentExtension.

After studying the code a bit more, I think I was worrying about some
corner cases involving shell type replacement; but they're not
interesting enough to justify making the main-line cases harder to work
with.  So I think this is a good fix, and I applied it with some comment
adjustments.
        regards, tom lane