pg_upgrade fix for pg_largeobject_metadata

The attached, applied patch preserves
pg_largeobject_metadata.relfrozenxid in pg_upgrade.

This is needed only in 9.1 because only 9.0 had this table and no one is
upgrading from a 9.0 beta to 9.0 anymore.  We basically don't backpatch
9.0 beta fixes at this point.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +