[Gecode] Some small quirks in abs and power

[Christian Schulte]

Hej Gabor,

there is a small quirk in abs and some bigger in power:

	abs: the post function for AbsBndEx is flawed. Just check what you
did!

	power: power is also defined on NEGATIVE numbers! Just to remind:
numbers can be also negative here!

There is another problem which has to do with tells in the constructor. The
way it is done doesn't work (must be my fault) as failure is not signaled!

Cheers
Christian

-- 
Christian Schulte, http://www.imit.kth.se/~schulte/