Test clang 5 on travis

.travis.yml

@@ -12,6 +12,16 @@ matrix:
           packages: ['g++-5', 'lcov', 'llvm-4.0', 'clang-4.0', 'libclang-4.0-dev']
       env: TOOLSET=g++-5 CPPAST_TEST_GCOV=ON LLVM_CONFIG_BINARY=/usr/bin/llvm-config-4.0
 
+    - os: linux
+      dist: trusty
+      sudo: false
+      compiler: gcc
+      addons:
+        apt:
+          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-trusty-5.0']
+          packages: ['g++-5', 'lcov', 'llvm-5.0', 'clang-5.0', 'libclang-5.0-dev']
+      env: TOOLSET=g++-5 LLVM_CONFIG_BINARY=/usr/bin/llvm-config-5.0
+
     - os: linux
       dist: trusty
       sudo: false