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: I25af4512f3e7198d03828a87bdca719cb7105d7b
Merge "Support building wheels (PEP-427)"