Extension of the integrator - more power functions

I have committed the code for the extension of the integrator to get more
results for power functions.

I have tried to implement the code in a way to do no changes of old results. But
I have introduced new noun forms for some results. 

I regognized that this is not a good idea by studying the Chapter 7: "Symbolic
Integration Tools" written by E. Woollett. In this paper integrals which are
only solved in parts are mentioned.

I have modified the code I have written in a way to return exactly all old
results and will commit it.

The best would be to do the integration of the power functions within the
routine intform, because that is the place pattern matching is widely used. But
when we introduce code at this place we change much to lot.

Dieter Kaiser