[security-services] Two issues on Advice

An engineer here just asked two questions which caused me to notice the 
following issues.  I don't expect them to get into core-27, but for the record:

- Minor: The Advice element schema (line 590 in core-26) has a sequence
   surrounding an unbounded choice.  I think the sequence element can be
   removed, as it has no impact.

- Major: Why do we go to the trouble of having an <AdviceElement> with
   an abstract type (so you have to use xsi:type) when we also allow
   ##any?  There is no incentive to derive a type from AdviceAbstractType
   when you can just supply whatever elements you want.  I think we could
   safely remove AdviceAbstractType and AdviceElement altogether.

	Eve
--
Eve Maler                                    +1 781 442 3190
Sun Microsystems XML Technology Center   eve.maler @ sun.com