Added fallback for stdbool.h on Windows using MSVC

There is no stdbool.h on Windows (With MSVC). I've worked around this for now by changing the template. I don't know if this is the best way to handle this or if there is a better solution (Fancier ifdefs? Include an stdbool.h? Leave it up to the developer to implement/include?) But this commit is currently working for me.