pgsql: pgbench: allow a script weight of zero

pgbench: allow a script weight of zero

This refines the previous weight range and allows a script to be "turned
off" by passing a zero weight, which is useful when scripting multiple
pgbench runs.

I did not apply the suggested warning when a script uses zero weight; we
use the principle elsewhere that if there's nothing to be done, do
nothing quietly.

Adjust docs accordingly.

Author: Jeff Janes, Fabien Coelho

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/a1c935d3b71e44ba36530d47c3ccab6cc9b9eafe

Modified Files
--------------
doc/src/sgml/ref/pgbench.sgml | 23 ++++++++++++-----------
src/bin/pgbench/pgbench.c | 13 ++++++++++---
2 files changed, 22 insertions(+), 14 deletions(-)