pgsql: Allow pg_upgrade to upgrade clusters that use exclusion contrain

Allow pg_upgrade to upgrade clusters that use exclusion contraints by
fixing pg_dump to properly preserve such indexes.

Backpatch to 9.1 and 9.0 (where the bug was introduced).

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/6b5510e8d64f9c76b1c24c46537d5a83a3483778

Modified Files
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src/bin/pg_dump/pg_dump.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)