[Dune] Dune on Windows MinGW

[Christian Engwer]

Hi Jö,

> I would suggest to use static member variables instead of functions, so the
> mathematical functions don't have to be evaluated each time a constant is
> needed.  I believe Christian discovered at one point that exp() could be quite
> expensive, and that is probably true for the other mathematical functions as
> well.  (Or was it pow()?)

That is nothing new, many of these mathematical operations have to be
implementation using some expansion series, thus their evaluation is
rather expensive.

Christian