[core] fix nanoseconds handling for Timestamps (#1020)
[core] fix nanoseconds handling for Timestamps (#1020)

Extracted from #1008, credit goes to @rdubya
kares/activerecord-jdbc-adapter,bruceadams/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,kares/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,bruceadams/activerecord-jdbc-adapter,bruceadams/activerecord-jdbc-adapter,kares/activerecord-jdbc-adapter