pg_upgrade:  remove support for 8.3 old clusters

This trims down the code, and is in preparation for hardening pg_upgrade
against auto-oid assignment.
revert "Throw error for ALTER TABLE RESET of an invalid option"

Reverts commits 73d78e11a0f7183c80b93eefbbb6026fe9664015 and
b0488e5c4fbfdce8acc989bdc17d9f0ec09ac281.  Also reverts pg_upgrade
changes.
pg_upgrade docs:  update docs for 8.3 support removal