[rt.cpan.org #54113] Add support for lo_truncate() function

[Greg Sabino Mullane via RT]

<URL: https://rt.cpan.org/Ticket/Display.html?id=54113 >

(re lo_truncate support)

> This is surprisingly tricky to get working. All the pieces are in
> place, but I cannot get to work without returning -1 (an error). Maybe
> I'll commit what I have.

This is in place if someone wants to take a crack at fixing it.