Inflater/Deflater improvements

[Clemens Eisserer]

Hi Martin,

> I think many people will be interested in performance improvements
> in Inflater/Deflater.  I may have time to help review.
>
> Caution: This is an area where it can be very tricky to make
> improvements.  Past efforts have optimized one usage pattern
> at the cost of pessimizing another.

I can't imagine a use-case where this version would perform a lot
worse, however a clear downside is for sure the larger amount of
C-heap consumed.
However the current implementation is so bad, it should be worth it ;)
I am more afraid of behaviour change in corner cases ...

Thanks, Clemens