pgsql: Have pg_upgrade properly preserve relfrozenxid in toast tables.

Have pg_upgrade properly preserve relfrozenxid in toast tables.

This fixes a pg_upgrade bug that could lead to query errors when clog
files are improperly removed.

Branch
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REL9_0_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/00bf707113a297aa85c38beda8fb1247fe4bd304

Modified Files
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src/bin/pg_dump/pg_dump.c |   36 +++++++++++++++++++++++++++++++++---
src/bin/pg_dump/pg_dump.h |    2 ++
2 files changed, 35 insertions(+), 3 deletions(-)