pgsql: Document why pg_upgrade preserves pg_auth.oid (because they are

Document why pg_upgrade preserves pg_auth.oid (because they are stored
in pg_largeobject_metadata).

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=133641a48eb9a3406fda7014a60fd42dfecfa089

Modified Files
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contrib/pg_upgrade/pg_upgrade.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)