Herbert Valerio Riedel authored Sep 20, 2017 and Oleg Grenrus committed Jan 16, 2018

This provides a provisional (i.e. hacky) retrofitted implementation of
the forward-compat scheme described in #4899 for the cabal-2.2 branch

This hack works by constructing a dummy package description in case
the package description fails to be parsed via the standard parser,
and we detect a new-style cabal-spec declaration.