Run the 2to3 ws_comma fixer on *.py files. Some lines are now too long
and will need to be broken at some point. OTOH, some lines were already
too long and need to be broken at some point. Now seems as good a time
as any to do this with open PRs at a minimum.

The f2py executable has a shebang which uses the default python, rather
than the python it was compiled for.  This causes issues for deployment
of numpy (+f2py) across systems which have different environments.

This fix uses sys.executable to determine the resulting hardcoded
python to use.

Add `print_function` to all `from __future__ import ...` statements
and use the python3 print function syntax everywhere.

Closes #3078.

This should be harmless, as we already are division clean. However,
placement of this import takes some care. In the future a script
can be used to append new features without worry, at least until
such time as it exceeds a single line. Having that ability will
make it easier to deal with absolute imports and printing updates.

Thanks to Lisandro Dalcin.

Rewrite F2Py's test suite, so that it is run as a part of Numpy's tests.
These tests require compiling extension modules on-the-fly, so I added
a small helper module for that.