Merge pull request #25 from Chainsawkitten/Clang3.5

Fix Travis Clang build

.travis.yml

@@ -8,10 +8,10 @@ os: linux
 env:
   - BUILD_TYPE=Debug EXTRA_CHECKS=ON TRACE=ON CXX_=g++-6 CC_=gcc-6 GR_BACKEND=GL
   - BUILD_TYPE=Release EXTRA_CHECKS=OFF TRACE=OFF CXX_=g++-6 CC_=gcc-6 GR_BACKEND=GL
-  - BUILD_TYPE=Debug EXTRA_CHECKS=ON TRACE=ON CXX_=clang++-3.7 CC_=clang-3.7 GR_BACKEND=GL
-  - BUILD_TYPE=Release EXTRA_CHECKS=OFF TRACE=OFF CXX_=clang++-3.7 CC_=clang-3.7 GR_BACKEND=GL
+  - BUILD_TYPE=Debug EXTRA_CHECKS=ON TRACE=ON CXX_=clang++-4.0 CC_=clang-4.0 GR_BACKEND=GL
+  - BUILD_TYPE=Release EXTRA_CHECKS=OFF TRACE=OFF CXX_=clang++-4.0 CC_=clang-4.0 GR_BACKEND=GL
   - BUILD_TYPE=Debug EXTRA_CHECKS=ON TRACE=ON CXX_=g++-6 CC_=gcc-6 GR_BACKEND=VULKAN
-  - BUILD_TYPE=Debug EXTRA_CHECKS=ON TRACE=ON CXX_=clang++-3.7 CC_=clang-3.7 GR_BACKEND=VULKAN
+  - BUILD_TYPE=Debug EXTRA_CHECKS=ON TRACE=ON CXX_=clang++-4.0 CC_=clang-4.0 GR_BACKEND=VULKAN
 
 cache:
   apt: true
@@ -19,12 +19,13 @@ cache:
 addons:
   apt:
     sources:
+      - llvm-toolchain-trusty-4.0
       - sourceline: 'ppa:ubuntu-toolchain-r/test'
       - sourceline: 'ppa:graphics-drivers/ppa'
     packages:
       - cmake
       - g++-6
-      - clang-3.5
+      - clang-4.0
       - libvulkan-dev
       - libegl1-mesa-dev