message: bumping the osx image for gcc 6/7/8 from a no-longer supported xcode 9.3 to the latest
diff: @@ -215,19 +215,19 @@ matrix:
  # OSX GCC 6
  - env: COMPILER=g++-6 HAS_ASAN_32=true HAS_UBSAN_32=true HAS_ASAN_64=true HAS_UBSAN_64=true
  compiler: gcc
  - osx_image: xcode9.3
  + osx_image: xcode10
  os: osx
  # OSX GCC 7
  - env: COMPILER=g++-7 HAS_ASAN_32=true HAS_UBSAN_32=true HAS_ASAN_64=true HAS_UBSAN_64=true
  compiler: gcc
  - osx_image: xcode9.3
  + osx_image: xcode10
  os: osx
  # OSX GCC 8
  - env: COMPILER=g++-8 HAS_ASAN_32=true HAS_UBSAN_32=true HAS_ASAN_64=true HAS_UBSAN_64=true
  compiler: gcc
  - osx_image: xcode9.3
  + osx_image: xcode10
  os: osx
  # OSX LLVM-GCC
  @@ -244,19 +244,19 @@ matrix:
  # OSX GCC 6
  - env: COMPILER=g++-6 HAS_ASAN_32=true HAS_UBSAN_32=true HAS_ASAN_64=true HAS_UBSAN_64=true
  compiler: gcc
  - osx_image: xcode9.3
  + osx_image: xcode10
  os: osx
  # OSX GCC 7
  - env: COMPILER=g++-7 HAS_ASAN_32=true HAS_UBSAN_32=true HAS_ASAN_64=true HAS_UBSAN_64=true
  compiler: gcc
  - osx_image: xcode9.3
  + osx_image: xcode10
  os: osx
  # OSX GCC 8
  - env: COMPILER=g++-8 HAS_ASAN_32=true HAS_UBSAN_32=true HAS_ASAN_64=true HAS_UBSAN_64=true
  compiler: gcc
  - osx_image: xcode9.3
  + osx_image: xcode10
  os: osx
  install:
  