[Distutils] Last PEP 426 update for a while

[Nick Coghlan]

I pushed a version of PEP 426 with an initial sketch of an entry
points replacement design: http://hg.python.org/peps/rev/ea3d93e40e02

To give it a sensible home in the PEP, I ended up defining "modules"
and "namespaces" fields in addition to "commands" and "exports". The
overall section is called "Installed interfaces".

I initially tried it with the unpacked multi-field mapping for export
specifiers, but ended up reverting to something closer to the
setuptools notation for readability purposes. For the moment,
"requires_extra" is included since it isn't that hard to explain.

The other two major additions to the PEP are a note near the top
explaining that the expected time frame for metadata 2.0 is post
Python 3.4 release and a caveat on the build system description
explaining that we know it isn't ready for prime-time yet.

I wanted to get this part up so anyone tinkering with wrapper scripts
had at least a preliminary scheme to work from, but as per the note on
time frames, I don't consider the details of PEP 426 to be an urgent
topic for further discussion unless/until it directly impacts next
generation tools like Warehouse and distlib.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia