message: Travis: Add xcode 9.1; Disable xcode 6.4, because download of qt for osx 10.10 times out.
diff: @@ -28,27 +28,27 @@ matrix:
  compiler: clang
  env: BUILD_TYPE=tsan BUILD_WITH=cmake COVERAGE=no
  - os: osx
  - osx_image: xcode6.4 # OS X 10.10
  + osx_image: xcode7.3 # OS X 10.11
  compiler: clang
  - env: BUILD_TYPE=normal BUILD_WITH=cmake COVERAGE=gcov
  + env: BUILD_TYPE=normal BUILD_WITH=cmake COVERAGE=llvm
  - os: osx
  - osx_image: xcode6.4 # OS X 10.10
  + osx_image: xcode7.3 # OS X 10.11
  compiler: clang
  - env: BUILD_TYPE=normal BUILD_WITH=autoconf COVERAGE=gcov
  + env: BUILD_TYPE=normal BUILD_WITH=autoconf COVERAGE=llvm
  - os: osx
  - osx_image: xcode7.3 # OS X 10.11
  + osx_image: xcode8.3 # macOS 10.12
  compiler: clang
  env: BUILD_TYPE=normal BUILD_WITH=cmake COVERAGE=llvm
  - os: osx
  - osx_image: xcode7.3 # OS X 10.11
  + osx_image: xcode8.3 # macOS 10.12
  compiler: clang
  env: BUILD_TYPE=normal BUILD_WITH=autoconf COVERAGE=llvm
  - os: osx
  - osx_image: xcode8.2 # macOS 10.12
  + osx_image: xcode9.1 # macOS 10.12
  compiler: clang
  env: BUILD_TYPE=normal BUILD_WITH=cmake COVERAGE=llvm
  - os: osx
  - osx_image: xcode8.2 # macOS 10.12
  + osx_image: xcode9.1 # macOS 10.12
  compiler: clang
  env: BUILD_TYPE=normal BUILD_WITH=autoconf COVERAGE=llvm
  - os: linux
  