ORDER BY is used

The range analysis module did not correctly signal to the 
handler that a range represents a ref (EQ_RANGE flag). This causes 
non-range queries like 
SELECT ... FROM ... WHERE keypart_1=const, ..., keypart_n=const 
ORDER BY ... FOR UPDATE
to wait for a lock unneccesarily if another running transaction uses
SELECT ... FOR UPDATE on the same table.

Fixed by setting EQ_RANGE for all range accesses that represent 
an equality predicate. 


mysql-test/r/innodb_mysql.result:
  bug#28570: Test Result
mysql-test/t/innodb_mysql.test:
  bug#28570: Test Case
sql/handler.cc:
  bug#28570: Updated comment
sql/opt_range.cc:
  bug#28570: Removed the criterion that key has to be unique (HA_NOSAME) in 
  order for the EQ_RANGE flag to be set. It is sufficient that the range 
  represent a ref access.