Support building wheels (PEP-427)

Universal is used to identify pure-Python module(by bdist_wheel). For
these, it is sufficient to build a wheel with _any_ Python ABI version
and publish that to PyPI (by whatever means).

Change-Id: Ibca65044d61d4b9b248013e4fe316f3c1a05f764
Merge "Support building wheels (PEP-427)"