message: construction_worker: added Clang 3.9-5.0
  Taken from
diff: @@ -207,6 +207,27 @@ matrix:
  env: LLVM_VERSION=3.8.1
  compiler: clang
  + - os: linux
  + addons:
  + apt:
  + sources: llvm-toolchain-trusty-3.9
  + packages: clang-3.9
  + env: COMPILER=clang++-3.9
  +
  + - os: linux
  + addons:
  + apt:
  + sources: llvm-toolchain-trusty-4.0
  + packages: clang-4.0
  + env: COMPILER=clang++-4.0
  +
  + - os: linux
  + addons:
  + apt:
  + sources: llvm-toolchain-trusty
  + packages: clang-5.0
  + env: COMPILER=clang++-5.0
  +
  #####################
  # installation step #
  #####################
  