Support the same set of extended math built-ins provided by the Python interpreter

[jathak]

The Python interpreter includes several additional math built-ins.

It would be nice to have functionality that more-or-less matches the Python version.

Since the built-ins in Python come directly from the Python math module, there's likely to be some variance between them and the corresponding functions in the dart:math library.

These built-ins should probably be added as a part of a separate SchemeLibrary, instead of adding them to the StandardLibrary