Log Message:
Update p5-DBD-postgresql to 1.21

      - System tables no longer returned by tables().
      - Fix table_attributes to handle removal of pg_relcheck in 7.3,
      - Properly reset transaction status after failed transaction when
        autocommit is off.  Properly report transaction failure message.
      - New pg_bool_tf database handle that when set to true booleans are
        returned as 't'/'f' rather than 1/0.
      - Maintenance transferred to GBorg.
      - Added implementations of column_info() and table_info(), and
        primary_key_info().
      - The POD formatting was cleaned up.
      - The preparser was updated to better handle escaped characters.
      - Added eg/lotest.pl as a demonstration of using large objects in buffers
        rather than files.
      - Added LISTEN/NOTIFY functionality.
      - Added constants for common PostgreSQL data types.
      - Fixed compile-time warnings.