net/py-pyzmq: update to 15.2.0

[novel]

Summary

Also, pyzmq now ships asyncio support that requires support of PEP 0409 [1]
and depends on asyncio. As PEP0409 is supported in Python 3.3+ and
asyncio is included into stdlib in 3.4, for 3.3 add dependency on devel/py-asyncio.

1: https://www.python.org/dev/peps/pep-0409/

Test Plan

Tested with poudriere on 11/10/9 amd64 and 10 i386.

[koobs]

Makefile

22 ↗

(On Diff #14027)

Better to use PYTHON_REL == 3300

[koobs]

Ignore that, == 3300 is incorrect.

>= 3300 && < 3400 is the most explicit