Re: add modulo (%) operator to pgbench

Three different modulo operators seems like a lot for a language that
doesn't even have a real expression syntax, but I'll yield to whatever
the consensus is on this one.

Here is a third simpler patch which only implements the Knuth's modulo, where the remainder has the same sign as the divisor.

I would prefer this version 3 (one simple modulo based on Knuth definition) or if there is a problem version 2 (all 3 modulos). Version 1 which provides a modulo compatible with C & SQL is really useless to me.