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: Ieabefc1fc8c8fbcd8749c07ccabb1ff88e1a761e
Merge "Support building wheels (PEP-427)"