pg_upgrade: allow upgrades for new-only TOAST tables

Previously, when calculations on the need for toast tables changed,
pg_upgrade could not handle cases where the new cluster needed a TOAST
table and the old cluster did not.  (It already handled the opposite
case.)  This fixes the "OID mismatch" error typically generated in this
case.

Backpatch through 9.2
In pg_dump, show server and pg_dump versions with or without --verbose.

We used to print this information only in verbose mode, but it's argued
that it's useful enough to print always; one reason being that this
provides some documentation about which Postgres versions the dump is
meant to reload into.

Jing Wang, reviewed by Jeevan Chalke
Fix typo in comment.

This typo was accidentally added by recent commit 4cbd128.