and value-list

The server returns unexpected results if a right side of the 
NOT IN clause consists of NULL value and some constants of
the same type, for example:

  SELECT * FROM t WHERE NOT t.id IN (NULL, 1, 2) 
  
may return 3, 4, 5 etc if a table contains these values.


The Item_func_in::val_int method has been modified:
unnecessary resets of an Item_func_case::has_null field 
value has been moved outside of an argument comparison
loop. (Also unnecessary re-initialization of the null_value
field has been moved).


mysql-test/r/func_in.result:
  Added test case for bug #37761.
mysql-test/t/func_in.test:
  Added test case for bug #37761.
sql/item_cmpfunc.cc:
  Bug #37761: IN handles NULL differently for table-subquery 
              and value-list
  
  The Item_func_in::val_int method has been modified:
  unnecessary resets of an Item_func_case::has_null field 
  value has been moved outside of an argument comparison
  loop. (Also unnecessary re-initialization of the null_value
  field has been moved).