Rename method as to not hide a base.
Reorder attributes initialization.
Remove unused variable.
Rework code to silence a warning due to assignment used as truth value.


sql/item_strfunc.cc:
  Rename method as to not hide a base.
sql/item_strfunc.h:
  Rename method as to not hide a base.
sql/log_event.cc:
  Reorder attributes initialization.
sql/rpl_injector.cc:
  Rework code to silence a warning due to assignment used as truth value.
sql/rpl_record.cc:
  Remove unused variable.
sql/sql_db.cc:
  Rework code to silence a warning due to assignment used as truth value.
sql/sql_parse.cc:
  Rework code to silence a warning due to assignment used as truth value.
sql/sql_table.cc:
  Rework code to silence a warning due to assignment used as truth value.