mysql-test/r/union.result:
  new tests, more correct results for old one
mysql-test/t/union.test:
  new tests, more correct results for old one
sql/field.cc:
  new way to make field types csting
sql/field.h:
  new way to make field types csting
sql/item.cc:
  new way to make field types csting
sql/sql_derived.cc:
  fixed typo
sql/sql_lex.h:
  comment added