mysql-test/r/ps.result:
  Added test coverage for "order by" in prepared statements (related to BUG#16474).
mysql-test/r/sp.result:
  Added reference to test case for BUG#16474.
mysql-test/t/ps.test:
  Added test coverage for "order by" in prepared statements (related to BUG#16474).
mysql-test/t/sp.test:
  Added reference to test case for BUG#16474.
sql/sql_select.cc:
  Fixed comment and test for basic_const_item() instead of is_splocal().