Drop AppVeyor

.appveyor.yml

@@ -1,28 +0,0 @@
-image: Visual Studio 2015
-
-environment:
-  matrix:
-    - MSYS2_ARCH: i686
-      MSYSTEM: MINGW32
-
-clone_depth: 10
-
-build_script:
-  - cd %APPVEYOR_BUILD_FOLDER%
-  - set PATH=C:\msys64\mingw32\bin;C:\msys64\usr\bin;%PATH%
-  - bash ./unixbuild.sh
-
-deploy:
-  provider: GitHub
-  force_update: true
-  auth_token:
-    secure: zSJnpSnrKY1NO5RPVBaD/uq7UPyc+GW7ecjPFqEMsLjtnd6H+iNfROdoeuxJgt5T
-  artifact: Binaries
-  prerelease: true
-  on:
-    appveyor_repo_tag: true
-
-artifacts:
-  - path: dist\**\*.zip
-    name: Binaries
-