innobase/lock/lock0lock.c:
  Made change where lock on the supremum record is really a 'gap' type lock and
  gap type lock do not need to wait if it is not LOCK_INSERT_INTENSION type.
innobase/row/row0ins.c:
  Added fuction row_ins_set_exclusive_rec_lock to set exclusive lock on a record. 
  This function is used for locking possible duplicate key records when
  user has issued REPLACE-command.
  
  Because manual defines the REPLACE semantics that it is either an INSERT or 
  DELETE(s) for duplicate key + INSERT, we take X-lock directly for duplicate
  records to avoid unnecessary lock upgrades and deadlocks caused by lock 
  upgrades.