Fix typo in resultproxy.c and test compatibility with python 3.5

Fix typo in resultproxy.c and test compatibility with python 3.5

- Fix typo in resultproxy.c that would error on windows.
- add -Wundef to C flags when linux is detected so that undefined
symbols emit a warning
- a few adjustments for tests to succeed on python 3.5
- note minimum version still documented here as 3.4 but this should
move to at least 3.5 if not 3.6 for SQLAlchemy 1.4

Change-Id: Ia93ee1cb5c52e51e72eb0a24c100421c5157d04b