chore: use newer version of libclang on CI

Author: bsteinb

.travis.yml

@@ -4,18 +4,21 @@ sudo: false
 
 addons:
   apt:
+    sources:
+      - ubuntu-toolchain-r-test
+      - llvm-toolchain-precise-3.9
     packages:
       # for building MPI libraries
       - build-essential
       - gfortran
       # bindgen dependency
-      - libclang-3.4-dev
+      - libclang-3.9-dev
 
 env:
   global:
     - RELEASE_LIBRARY=mpich
     - RELEASE_LIBRARY_VERSION=3.2
-    - LIBCLANG_PATH=/usr/lib/llvm-3.4/lib
+    - LIBCLANG_PATH=/usr/lib/llvm-3.9/lib
     # GH_TOKEN=...
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     # CRATES_IO_TOKEN=...