Changed pointer arithmetic type to use unsigned long. Those are large enough

Building on i386 produced compiler warnings indicating that the previously-used
type was too small
Resolved alignent issues due to null or non-physical input

Normally PP handles null output piddles or non-physical inputs. I, however, need
to have piddles ready at plan-making time, which is before PP sees the data. I
thus handle these myself. As a result, the plan made by FFTW is guaranteed to be
usable by FFTW later on
skipping plan-creation checks

If I assume that pdl memory is aligned then I can predict when plans will be
made. Otherwise I cannot, so I disable those tests
added a threaded test where each thread element has a different alignment

This should cause issues with the current architecture, where a single plan is
created for each thread block. I'm not seeing any issues, however....