[Distutils] Officially deferring the Metadata 2.0 specification

[Nick Coghlan]

Metadata 2.0 has been deferred-in-practice for quite some time, but I
just updated the PEP itself to reflect the deferral and link to more
of the incremental improvement PEPs:
https://hg.python.org/peps/rev/94c1afae202e

This makes the current policy that enhancement proposals should avoid
depending on the definition and implementation of metadata 2.0
explicit.

Regards,
Nick.

P.S. PEP 459 (standard metadata extensions) depends on 426, and has
also been marked as Deferred

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