Send bytea values in "escape" format to old servers
Don't look at AffectedRows in SELECT for pre-9.0 servers

It looks like the number of rows affected by SELECT was not part of
the command tag before version 9.0, though I can't see a mention of
it in the release notes.
Don't try to run TestByteaOutputFormats against old servers
Remove usage of DO in test cases
Add tests for 8.4