The external 'for' loop in remove_dup_with_compare() handled 
HA_ERR_RECORD_DELETED by just starting over without advancing 
to the next record which caused an infinite loop. 
 
This condition could be triggered on certain data by a SELECT 
query containing DISTINCT, GROUP BY and HAVING clauses. 

Fixed remove_dup_with_compare() so that we always advance to 
the next record when receiving HA_ERR_RECORD_DELETED from 
rnd_next(). 

mysql-test/r/distinct.result:
  Added a test case for bug #46159.
mysql-test/t/distinct.test:
  Added a test case for bug #46159.
sql/sql_select.cc:
  Fixed remove_dup_with_compare() so that we always advance to 
  the next record when receiving HA_ERR_RECORD_DELETED from 
  rnd_next().