[postgres] sync a bit with Rails, drop support for older DBs
[postgres] sync a bit with Rails, drop support for older DBs

* Have supports_x? in the same order
* insert_returning is on unless configured off
* remove standard_conforming_strings stuff, non-standard conforming
  strings haven't been working in since 50.x anyways and it would
  only matter for ancient versions of PG (<9.x)
* unlike Rails, support for 9.2 (EOL) left intact
* only use hex-escaped bytea, i.e. drop support for <9.0

bruceadams/activerecord-jdbc-adapter,bruceadams/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,kares/activerecord-jdbc-adapter,kares/activerecord-jdbc-adapter,bruceadams/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,kares/activerecord-jdbc-adapter