SRF returned records must match expected type about plv8 HOT 5 CLOSED

I've got an error with the repro.

db1=#  select * from xxx(3) as x(x int); 
ERROR:  invalid memory alloc request size 136899977152

We need to fix it anyway.

I think I've fixed it with ffc7b31e47482c31ffbf956007ff470f79c20732.
Please make sure it's what you expected.

Yes, it's better, but not quite what we need yet. If the expected names don't 
match the actual field names, then an error should be thrown. Here's what 
plperl does:

andrew=# create or replace function xxx_perl(n int) returns setof record 
language plperl as 
    $x$ my $n = shift; for (my $i=0; $i<$n; $i++) { return_next({"n" => $i*2}) }; $x$;
CREATE FUNCTION
andrew=# select * from xxx_perl(3) as x(x int);
ERROR:  Perl hash contains nonexistent column "n" at line 1.
CONTEXT:  PL/Perl function "xxx_perl"
andrew=# 

Partial fix committed. Now the number of sattributes is checked. Still to do is 
the name comparisons - the code is all there apart from the actual comparison.

We'll also need some regression tests for this.

Fix completed, and regression tests added.