message: Switch travis distribution from trusty (14.04) to bionic (18.04)
diff: # Build Configuration for Travis CI
  # https://travis-ci.org
  -dist: trusty
  +dist: bionic
  language: cpp
  matrix:
  @@ -68,18 +68,17 @@ matrix:
  - sudo apt-get update
  - sudo apt-get purge g++
  - sudo apt-get install g++-6
  - - sudo apt-get install clang-3.6
  - - CC=clang-3.6 && CXX=clang++-3.6
  + - sudo apt-get install clang-3.9
  + - CC=clang-3.9 && CXX=clang++-3.9
  addons:
  apt:
  sources:
  - ubuntu-toolchain-r-test
  - - llvm-toolchain-trusty-3.6
  packages:
  - ninja-build
  - xorg-dev
  - libglu1-mesa-dev
  - compiler: clang++-3.6
  + compiler: clang++-3.9
  - os: linux
  before_install:
  