* Some changes to make the project completely compatible to MSVC11 (VS2012)

Dear ndarray maintainers,

I just made four little changes to get the project compile without warnings on MSVC11. I'd be glad if you incorporate them.

Best,
Christoph
This is the only change that concerns me, because it's the way the SCons docs say we should refer to a path that's relative to the SConstruct directory:
http://www.scons.org/doc/production/HTML/scons-user.html#idp4580896

This definitely doesn't work on Windows?