Re: BUG #2683: spi_exec_query in plperl returns column names which are not marked as UTF8

I wrote:
> It looks to me like basically everywhere in plperl.c that does newSVpv()
> should follow it with
>
> #if PERL_BCDVERSION >= 0x5006000L
> if (GetDatabaseEncoding() == PG_UTF8)
> SvUTF8_on(sv);
> #endif

Experimentation proved that this was insufficient to fix Vitali's
problem --- the string he's unhappy about is actually a hash key entry,
and there's no documented way to mark the second argument of hv_store()
as being a UTF-8 string. Some digging in the Perl source code found
that since at least Perl 5.8.0, hv_fetch and hv_store recognize a
negative key length as meaning a UTF-8 key (ick!!), so I used that hack.
I am not sure there is any reasonable fix available in Perl 5.6.x.

Attached patch applied to HEAD, but I'm not going to risk back-patching
it without some field testing.

regards, tom lane