Honor stringtype=unspecified when also saving null values
Merge pull request #223 from byronvf/master

Honor stringtype=unspecified when also saving null values

Currently, saving a string with setString applies oid.UNSPECIFIED, but saving null with setNull(index, java.sql.Types.VARCHAR) saves with oid.VARCHAR.

For consistency, if the user requested that we treat string types as unspecified, we should do so in all cases.