Add changes missing from previous commit

These changes should have been part of a2d5fa1

.travis.yml

@@ -49,7 +49,7 @@ before_install:
 # - if [[ $TRAVIS_OS_NAME == osx                                                    ]]; then export CMAKE_CXX_FLAGS="${CMAKE_CXX_FLAGS} -fvisibility=hidden -fvisibility-inlines-hidden"       ; fi # This was an attempt to remove warnings like: "direct access in [...] to global weak symbol [...] means the weak symbol cannot be overridden at runtime" but none of "-fvisibility=default", "-fvisibility=hidden" or "-fvisibility=hidden -fvisibility-inlines-hidden" worked
   - if [[ $TRAVIS_OS_NAME == linux                                                  ]]; then export BUILD_FILE_SUFFIX="ubuntu14.04"; else export BUILD_FILE_SUFFIX="macos"                     ; fi
   - if [[ $TRAVIS_OS_NAME == linux ]] && [[ $CC =~ ^clang                           ]]; then export CXX="clang++-4.0" CC="clang-4.0"                                                           ; fi
-  - if [[ $TRAVIS_OS_NAME == linux ]] && [[ $CC =~ ^gcc                             ]]; then export CXX="g++-6"   CC="gcc-6"                                                                   ; fi
+  - if [[ $TRAVIS_OS_NAME == linux ]] && [[ $CC =~ ^gcc                             ]]; then export CXX="g++-4.9" CC="gcc-4.9"                                                                 ; fi
 # - if [[ $TRAVIS_OS_NAME == osx   ]] && [[ $CC =~ ^gcc                             ]]; then export CXX="g++-4.8" CC="gcc-4.8"                                                                 ; fi # Default gcc on osx is just a front-end for LLVM so should be able to use this to explicitly request the real GCC 4.8. It isn't working right now - maybe just needs a more recent osx_image (https://docs.travis-ci.com/user/reference/osx/#OS-X-Version) ? Not worth spending more time on now.
   - if [[ $BUILDTYPE =~ SAN$                                                        ]]; then export CMAKE_BUILD_TYPE="RELEASE"                                                                 ; fi
   - if [[ $BUILDTYPE == ASAN                                                        ]]; then export CMAKE_CXX_FLAGS="${CMAKE_CXX_FLAGS} -fsanitize=address -fno-omit-frame-pointer"            ; fi