pgsql: pg_dump: Add appropriate version check

pg_dump: Add appropriate version check

Some code added by commit 2f094e7ac69 needs to be behind a version
check so that it is not run against older databases.

Author: Andrew Dunstan <andrew@dunslane.net>
Reviewed-by: Junwang Zhao <zhjwpku@gmail.com>
Discussion: https://www.postgresql.org/message-id/afe3f099-3271-4fc4-8e32-467b5309affb%40dunslane.net

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/182cdf5aeaf7b34a288a135d66f2893dc288a24e

Modified Files
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src/bin/pg_dump/pg_dump.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)