Fix wrong usage of constant which could cause mysqld to use index when doing...

Fix wrong usage of constant which could cause mysqld to use index when doing an update/delete on small tables.
code cleanup


Docs/manual.texi:
  changelog
sql/ha_innobase.cc:
  Removed compiler warning
sql/slave.cc:
  Cleanup comments and indentation for suppressing connect warnings
sql/sql_db.cc:
  clean up comment
sql/sql_delete.cc:
  Fix wrong usage of constant which could cause mysqld to use index when doing an update/delete on small tables.
sql/sql_update.cc:
  Fix wrong usage of constant which could cause mysqld to use index when doing an update/delete on small tables.