pgsql: Correct overflow handling in pgbench.

Correct overflow handling in pgbench.

This patch attempts, although it's quite possible there are a few
holes, to properly detect and reported signed integer overflows in
pgbench.

Author: Fabien Coelho
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/20171212052943.k2hlckfkeft3eiio@alap3.anarazel.de

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/92a0342a90b38b0b007f079d33286f9aefabfe40

Modified Files
--------------
doc/src/sgml/ref/pgbench.sgml                |   7 ++
src/bin/pgbench/exprparse.y                  |   6 +-
src/bin/pgbench/exprscan.l                   |  21 +++-
src/bin/pgbench/pgbench.c                    | 137 +++++++++++++++++++--------
src/bin/pgbench/pgbench.h                    |   3 +-
src/bin/pgbench/t/001_pgbench_with_server.pl |  42 ++++----
src/bin/pgbench/t/002_pgbench_no_server.pl   |  16 ++++
7 files changed, 174 insertions(+), 58 deletions(-)