pgsql: Change pg_dump default for statistics export.

Change pg_dump default for statistics export.

Set the default behavior of pg_dump and pg_dumpall to be
--no-statistics.

Leave the default for pg_restore and pg_upgrade to be
--with-statistics.

Discussion: https://postgr.es/m/CA+TgmoZ9=RnWcCOZiKYYjZs_AW1P4QXCw--h4dOLLHuf1Omung@mail.gmail.com
Reviewed-by: Greg Sabino Mullane <htamfids(at)gmail(dot)com>
Reviewed-by: Nathan Bossart <nathandbossart(at)gmail(dot)com>
Reviewed-by: Robert Haas <robertmhaas(at)gmail(dot)com>
Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/34eb2a80d5a3ea1392e4a9f16ebac54e96d0c6ed

Modified Files
--------------
doc/src/sgml/ref/pg_dump.sgml | 20 ++++++------
doc/src/sgml/ref/pg_dumpall.sgml | 20 ++++++------
src/bin/pg_dump/pg_backup_archiver.c | 2 +-
src/bin/pg_dump/t/002_pg_dump.pl | 59 ++++++++++++++++++++++++++++++++++++
src/bin/pg_upgrade/dump.c | 2 +-
5 files changed, 81 insertions(+), 22 deletions(-)