Auto merge of #1210 - emilio:travis-maybe, r=<try>

bors-servo · web-flow · commit 63d6bedef0e5 · 2018-01-03T18:24:28.000-06:00
s/gcc/g++ in the travis deps Per https://docs.travis-ci.com/user/languages/cpp/, though not super-confident this will fix it.
diff --git a/.travis.yml b/.travis.yml
@@ -5,7 +5,7 @@ addons:
     sources:
       - ubuntu-toolchain-r-test
     packages:
-      - gcc-5
+      - g++-5
 
 os:
   - linux
