Message 106462 - Python tracker

Thanks for reviewing!

Updated patch, that addresses points 1-3.  For 4, there's no need for the old code, since "self - divmod_near(self, 10**-n)[1]" is enough.  And I didn't like the old algorithm anyway;  the new one is more straightforward.  For 5, I've added a Python version of divmod_near to the comments.