When handling DELETE ... FROM if there is no
condition it is internally transformed to 
TRUNCATE for more efficient execution by the
storage handler.
The check for validity of the optional ORDER BY 
clause is done after the check for the above 
optimization and will not be performed if the
optimization can be applied.
Moved the validity check for ORDER BY before 
the optimization so it performed regardless of
the optimization.


mysql-test/r/delete.result:
  Bug #26186: test case
mysql-test/t/delete.test:
  Bug #26186: test case
sql/sql_delete.cc:
  Bug #26186: do validity check of the ORDER BY
  before deciding to skip it.