Set SDK_PATH_HINTS to find the SDK better on windows.

This change makes the module work for me on Windows7 with Arduino 1.0.5 and Visual Studio 2012 (for nmake).

I have problems with getting the sdk find the path on windows, trying to set it as input to Cmake, became an escape hell as "C:\\Program Files (x86)\\Arduino" had to many strange features in it for the environment. both spaces () and \ i think the \ could be swaped for / as cmake is quite smart.