Re: PATCH: psql tab completion for SELECT

And here's a patch to add savepoint protection for tab completion.

It could definitely use some scrutiny to make sure it's not messing up
the user's transaction.

I added some error checking for the savepoint creation and the
rollback, and then wrapped it in #ifdef NOT_USED (just as the query
error checking is) as I wasn't sure how useful it is for normal use.

But I do feel that if psql unexpectedly messes up the transaction, it
should report it somehow.  How can we tell that we've messed it up for
the user?

Cheers,
Edmund