Re: pgbench - add pseudo-random permutation function

> Indeed, the patch needs a rebase & conflit resolution. I'll do it. Later.

Here is an update:

- take advantage of pg_bitutils (although I noted that the "slow"
popcount there could be speeded-up and shorten with a bitwise operator
implementation that I just removed from pgbench).

- add comments about the bijective transformations in the code.

As already stated, this function makes sense for people who want to test
performance with pgbench using non uniform rands. If you do not want to do
that, you will probably find the function pretty useless. I can't help it.

Also, non uniform rands is also a way to test pg lock contention behavior.

--
Fabien.