gflags support

[fmoo]

It's common to use py wrapped cpp libraries that use gflags.

Build a bridge to expose any gflags defined in this way theough argparse, and preferably the options interfaces as well

[fmoo]

Though there are plenty of open source Python solutions that expose gflags-like global option declaration, it looks like there's no solution for shared library/extension dependencies that leverage libgflags proper.

For fun a week ago I implemented a proof of concept in cython that solves this, but we have an internal solution that uses boost::python that is more well-tested and complete that I'd like to open source instead.