Auto merge of #3775 - alexcrichton:version-info, r=alexcrichton
authorbors <bors@rust-lang.org>
Wed, 1 Mar 2017 03:36:24 +0000 (03:36 +0000)
committerbors <bors@rust-lang.org>
Wed, 1 Mar 2017 03:36:24 +0000 (03:36 +0000)
Prefer CARGO_PKG_* in version info

These are always set by Cargo and avoids rustbuild-building-cargo to need to
parse semver


Trivial merge