Misc/NEWS.d/next/Library/2018-05-12-06-01-02.bpo-33453.Fj-jMD.rst

Fix dataclasses to work if using literal string type annotations or if using
PEP 563 "Postponed Evaluation of Annotations".  Only specific string
prefixes are detected for both ClassVar ("ClassVar" and "typing.ClassVar")
and InitVar ("InitVar" and "dataclasses.InitVar").