When add an aliase name after NAME_CONST, the aliase name will be overwrite.
      
NAME_CONST will re-set the field's name only if there isn't an aliase in the
function fix-fields().
If there is an aliase, NAME_CONST doesn't re-set the field's name and keeps the old
name.

mysql-test/r/func_misc.result:
  Test result.
mysql-test/r/rpl_name_const.result:
  Test case.
mysql-test/t/func_misc.test:
  Add NAME_CONST test.
mysql-test/t/rpl_name_const.test:
  Test result.
sql/item.cc:
  Re-set field's name if the name is autogenerated, that mean without aliase.