security/py-libnacl: Update to 1.4.3

• Update to 1.4.3
• Patch setup.py so test command is supported
• Add regression-test target

Changes:

https://libnacl.readthedocs.org/en/latest/topics/releases/1.4.3.html

Based on:

PR: 200830
Submitted by: Christer Edwards <christer dot edwards gmail com>