SCons change to build a static lib for Windows

Hi Devteam,

I just added a few lines to the library SCons file, so that a static library is built for Windows.

Building a shared library would require __declspec(dllexport) and the respective dllimport declarations for all exported methods. This currently requires more time than I can invest, so I decided to build a static version. I'd be happy if you include it, so that the library can be used on Windows as well!

Best,
Christoph