Test C++17 mode in travis

.travis.yml

@@ -31,6 +31,10 @@ matrix:
         env: |
             label="gcc 32 bit C++11";
             user_config="using gcc : : g++-4.8 -m32 -fsanitize=address -Werror --std=c++11 ;"
+      - compiler: clang
+        env: |
+            label="clang C++17";
+            user_config="using clang : : clang++ -fsanitize=address -Werror --std=c++17 ;"
       - compiler: clang
         env: |
             label="clang C++11";