message: appveyor: try to run on more than one core
  Appveyor CI should provide 2 cores, so we can make use of that.
diff: @@ -41,6 +41,7 @@ before_build:
  build: on
  build_script:
  + - set CL=/MP
  - call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars64.bat"
  - cd curl-7.56.1\winbuild
  - if "%configuration%"=="Debug" (
  