Auto merge of #4955 - sfackler:allow-package, r=alexcrichton
authorbors <bors@rust-lang.org>
Thu, 18 Jan 2018 19:02:11 +0000 (19:02 +0000)
committerbors <bors@rust-lang.org>
Thu, 18 Jan 2018 19:02:11 +0000 (19:02 +0000)
Allow packaging of crates with unstable features

We don't want them to land on crates.io, but it's fine to make a .crate
file.

Closes #4954


Trivial merge