Add get_distutil_options(); future setup.py files can use this to check

Add get_distutil_options(); future setup.py files can use this to check
   whether the Distutils being used supports a particularly capability.

   (This idea was originally suggested by Juergen Hermann as a method
    on the Distribution class.  I think it makes more sense as a
    function in core.py, and that's what this patch implements.)