[PATCH] Use correct types and limits for PL/Perl SPI query results

Hi hackers,

Commit 23a27b039d94ba359286694831eafe03cd970eef changed the type of
numbers-of-tuples-processed counters to uint64 and adjusted various PLs
to cope with this. I noticed the PL/Perl changes did not take full
advantage of what Perl is capable of handling, so here's a patch that
improves that.

1) Perl's integers are at least pointer-sized and either signed or
unsigned, so can potentially hold up to 2⁶⁴-1. Floating point numbers
can also be larger than double (up to 128bit), allowing for exact
representation of integers beyond 2⁵³. Hence, adjust the setting of
the "processed" hash item to use UV_MAX for the limit and (NV) or
(UV) for the casts.

2) Perl 5.20 and later use SSize_t for array indices, so can cope with
up to SSize_t_max items in an array (if you have the memory).

3) To be able to actually return such result sets from sp_exec_query(),
I had to change the repalloc() in spi_printtup() to repalloc_huge().

--
"A disappointingly low fraction of the human race is,
at any given time, on fire." - Stig Sandbeck Mathisen