mysql-test/r/subselect.result:
  A warning added to subselect test due to the recent changes.
  
  UNION in sub-select returns the empty set, which is why this warning is
  a mistery to me.
mysql-test/r/union.result:
  two changes.
  
  First one is due to the proper handling of LIMIT offset, limit in 
  UNION without all.
  
  Second is a change in behaviour due to the fact that ORDER by in a 
  UNION without braces is not now applicable to the last SELECT node.
  
  It can not be applied until one bug is fixed (after my vacation).
  
  Should be documented.