auto merge of #13029 : FlaPer87/rust/master, r=alexcrichton

This should prevent lot of doc errors in Rust's buildbot and it shouldn't take long to run on travis. We could probably limit it to `std` but I preferred to just check all docs in this phase too.

@alexcrichton r?

Author: bors

.travis.yml

@@ -41,7 +41,7 @@ script: |
   fi &&
   make tidy &&
   make -j4 rustc-stage1 &&
-  make check-stage1-std check-stage1-rpass check-stage1-cfail check-stage1-rfail
+  make check-stage1-std check-stage1-rpass check-stage1-cfail check-stage1-rfail check-stage1-doc
 
 env:
   global: