Re: Centralizing protective copying of utility statements

I wrote:
> What seems like a much safer answer is to make the API change noisy.
> That is, move the responsibility for actually calling copyObject
> into ProcessUtility itself, and add a bool parameter saying whether
> that needs to be done. That forces all callers to consider the
> issue, and gives them the tool they need to make the right thing
> happen.

Here's a v2 that does it like that. In this formulation, we're
basically hoisting the responsibility for doing copyObject up into
ProcessUtility from its direct children, which seems like a clearer
way of thinking about what has to change.

We could avoid the side-effects on users of ProcessUtility_hook by
doing the copy step in ProcessUtility itself rather than passing the
flag on to standard_ProcessUtility. But that sounded like a bit of a
kluge. Also, putting the work in standard_ProcessUtility preserves
the option to redistribute it into the individual switch arms, in case
anyone does find the extra copying overhead annoying for statement
types that don't need it. (I don't plan to do any such thing as part
of this bug-fix patch, though.)

Barring objections, I'm going to push this into HEAD fairly soon,
since beta2 is hard upon us. Still thinking about which way to
fix it in the back branches.

regards, tom lane