update statements
      
Only SELECT statements report any examined rows in the slow
log. Slow UPDATE, DELETE and INSERT statements report 0 rows
examined, unless the statement has a condition including a
SELECT substatement.
      
This patch adds counting of examined rows for the UPDATE and
DELETE statements. An INSERT ... VALUES statement will still 
not report any rows as examined.



sql/sql_class.h:
  Added more docs for THD::examined_row_count.
sql/sql_delete.cc:
  Add incrementing thd->examined_row_count.
sql/sql_update.cc:
  Add incrementing thd->examined_row_count.