Auto merge of #4402 - bluss:doc-rustdocflags, r=alexcrichton
authorbors <bors@rust-lang.org>
Sun, 13 Aug 2017 12:40:53 +0000 (12:40 +0000)
committerbors <bors@rust-lang.org>
Sun, 13 Aug 2017 12:40:53 +0000 (12:40 +0000)
Document `RUSTDOCFLAGS`

Documentation for this environment variable was missing. It's supported in stable releases of Rust already.


Trivial merge