HPCC-10189 Add a flag to indicate a row in a self-join never matches itself

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #5180 from ghalliday/issue10189

HPCC-10189 Add a flag to indicate a row in a self-join never matches itself

Reviewed-By: Jamie Noss <james.noss@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>