Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Use print as a function for Python 3 [PEP 3105]

Import print_function from the __future__ module
to activate this for Python 2. This works as far back as Python 2.6.0a2:
https://docs.python.org/2/library/__future__.html

[PEP 3105] https://www.python.org/dev/peps/pep-3105/

Covert regression test to python 3

Approved by: cperciva
MFC after: 3 days

This is a regression test to verify the proper behavior of IP ID generation
code. It will push 200000 packets, then report back what the min and max
periods it saw for different IDs were.