pgsql: vacuumdb: Add --dry-run.

vacuumdb: Add --dry-run.

This new option instructs vacuumdb to print, but not execute, the
VACUUM and ANALYZE commands that would've been sent to the server.

Author: Corey Huinker <corey(dot)huinker(at)gmail(dot)com>
Reviewed-by: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>
Reviewed-by: Kirill Reshke <reshkekirill(at)gmail(dot)com>
Reviewed-by: Álvaro Herrera <alvherre(at)kurilemu(dot)de>
Discussion: https://postgr.es/m/CADkLM%3DckHkX7Of5SrK7g0LokPUwJ%3Dkk8JU1GXGF5pZ1eBVr0%3DQ%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d107176d27c73ea3589b949dde07b6bc38b8f583

Modified Files
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doc/src/sgml/ref/vacuumdb.sgml | 10 ++++++++++
src/bin/scripts/t/100_vacuumdb.pl | 12 ++++++++++++
src/bin/scripts/vacuumdb.c | 9 +++++++++
src/bin/scripts/vacuuming.c | 30 ++++++++++++++++++++----------
src/bin/scripts/vacuuming.h | 1 +
5 files changed, 52 insertions(+), 10 deletions(-)