fixing tests accordingly
item.cc:
  Allow mixing non-binary collation and binary collation
  even if coercibility is the same. 
  For easier 4.0 -> 4.1 migrating.


sql/item.cc:
  Allow mixing non-binary collation and binary collation
  even if coercibility is the same. 
  For easier 4.0 -> 4.1 migrating.
mysql-test/t/union.test:
  fixing tests accordingly
mysql-test/r/union.result:
  fixing tests accordingly
mysql-test/t/ctype_collate.test:
  fixing tests accordingly
mysql-test/r/ctype_collate.result:
  fixing tests accordingly