pg_upgrade patches applied

I have applied the attached four patches which simplify pg_upgrade
processing --- less code means fewer bugs.  The commit message is at the
top of each patch.

The last patch fixes a problem where I was not migrating
pg_largeobject_metadata and its index for 9.0+ migrations, which of
course would only affect migrations to 9.1 and 9.0 to 9.0 migrations, so
I backpatched that to 9.0.

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

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