message: trying to add a VS 2017 build
diff: # http://www.appveyor.com/docs/appveyor-yml
  +image: Visual Studio 2017
  +
  notifications:
  - provider: Email
  on_build_status_changed: false
  @@ -81,6 +83,13 @@ build_script:
  - msbuild all.sln /p:Configuration=%Configuration%;Platform=%arch% /maxcpucount
  - ctest -C %configuration% --output-on-failure
  - cd ..
  + - mkdir 2017
  + - cd 2017
  + - set gen=Visual Studio 15 2017%VS_GEN%
  + - cmake .. -G "%gen%"
  + - msbuild all.sln /p:Configuration=%Configuration%;Platform=%arch% /maxcpucount
  + - ctest -C %configuration% --output-on-failure
  + - cd ..
  # ============= MINGW - always 64 bit
  - mkdir gcc6
  - cd gcc6
  