bug#7839 ncorrect collation for char(ascii('a'))


sql/item_strfunc.cc:
  bug#7839 ncorrect collation for char(ascii('a'))
mysql-test/r/func_str.result:
  bug#7839 ncorrect collation for char(ascii('a'))
mysql-test/r/user_var.result:
  bug#7839 ncorrect collation for char(ascii('a'))