Auto merge of #5292 - djc:feature-requirements, r=alexcrichton
authorbors <bors@rust-lang.org>
Wed, 4 Apr 2018 18:58:15 +0000 (18:58 +0000)
committerbors <bors@rust-lang.org>
Wed, 4 Apr 2018 18:58:15 +0000 (18:58 +0000)
Revert serialization of features to string type

Accidentally broken during #5270 and only noticed after merge.

cc @matklad @Eh2406


Trivial merge