* 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 very line works on Windows as well. However, the main SConstruct file of the project and the top level SConscript do not. :(

I am currently using my main SConstruct file to initialize the build and configure the environment, and then just use the SConscript in the include folder to build its contents. This is, why my build breaks if the "#m4" version is used.

This personal reason, of course, is no reason to change the general package contents. However, I thought it would be good practice to use relative paths in the SConscript files to make just this portability possible. That's why I changed the line.

Feel free to handle the change at your liking: the line definitely works on Windows. I created the SConsChecks project, which is heavily inspired by your boost.numpy build system (https://github.com/ChrislS/SConsChecks) but works platform independent. If I have time, I might propose a platform independent SConstruct file for boost.numpy, making these problems obsolete.