py-cares netbsd-9 breakage, g/cing PYCARES_CFFI

[Greg Troxel <gdt%lexort.com@localhost>]

If anyone is using py-cares on netbsd-9, or anything that depends on it,
see the comments I just added.  Basically because of changes in either
py-cares or cffi, it's been broken, and remains broken.


Separately, py-cares has had

  MAKE_ENV+=      PYCARES_CFFI=1

for a long time.  As far as I can tell this used to switch pycares from
hand-written glue code to cffi-based glue code, and now cffi is the only
method.  Thus this environment variable should be dropped.  I'll do that
no sooner than Tuesday 12Z unless someone exlains why that's confused.