[postgres] supports_validate_constraints? (#944)
[postgres] supports_validate_constraints? (#944)

Fixes:
* rails52/test/cases/migration/foreign_key_test.rb
bruceadams/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,kares/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,kares/activerecord-jdbc-adapter,bruceadams/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,kares/activerecord-jdbc-adapter,bruceadams/activerecord-jdbc-adapter