message: ci: add clang-format-5.0
  This change just adds the binary. I will use the new image and make the format
  fixes in a follow up change.
diff: @@ -5,12 +5,12 @@ set -e
  # Setup basic requirements and install them.
  apt-get update
  apt-get install -y wget software-properties-common make cmake git python python-pip \
  - clang-format-3.6 bc libtool automake zip time golang g++ gdb strace
  + bc libtool automake zip time golang g++ gdb strace
  # clang head (currently 5.0)
  wget -O - http://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -
  apt-add-repository "deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial main"
  apt-get update
  -apt-get install -y clang-5.0
  +apt-get install -y clang-5.0 clang-format-5.0
  # Bazel and related dependencies.
  apt-get install -y openjdk-8-jdk curl
  echo "deb [arch=amd64] http://storage.googleapis.com/bazel-apt stable jdk1.8" | tee /etc/apt/sources.list.d/bazel.list
  