Test g++-7, and display output from hash_info

.travis.yml

@@ -14,6 +14,16 @@ matrix:
         env: |
             USER_CONFIG="using gcc : : g++-4.8 -Werror ;"
             CXXSTD=03,11
+      - compiler: g++-7
+        env: |
+            USER_CONFIG="using gcc : : g++-7 -Werror ;"
+            CXXSTD=11,14,17
+        addons:
+          apt:
+            packages:
+              - g++-7
+            sources:
+              - ubuntu-toolchain-r-test
       - compiler: clang
         env: |
             USER_CONFIG="using clang : : clang++ -Werror ;"
@@ -64,4 +74,5 @@ before_script:
 
 script:
     - cd ${TRAVIS_BUILD_DIR}/test
+    - ${HOME}/opt/bin/b2 --verbose-test -j 3 cxxstd=$CXXSTD -q ${BJAM_TOOLSET} include=${BOOST_ROOT} include=${TRAVIS_BUILD_DIR}/include hash_info
     - ${HOME}/opt/bin/b2 -j 3 cxxstd=$CXXSTD -q ${BJAM_TOOLSET} include=${BOOST_ROOT} include=${TRAVIS_BUILD_DIR}/include