Extension of normal messages with additional information

When the DBTXT option is active, additional fields are inserted in regular IEBCOPY messages. For example, message:

IEB120I <dd_name> VALIDATION ERROR

becomes:

IEB120I <dd_name> VALIDATION ERROR AT OFFSET X'hhhh' X'oooo'

where hhhh and oooo are offsets into the module (IEBDV0) detecting the error.