Merge pull request boostorg#775 from Flamefire/appveyor

Remove unsupported compilers from Appveyor

Author: djowel

.appveyor.yml

@@ -21,9 +21,6 @@ environment:
     - { APPVEYOR_BUILD_WORKER_IMAGE: 'Visual Studio 2019', ADDRMDL: 64, TOOLSET: 'msvc-14.2' }
     - { APPVEYOR_BUILD_WORKER_IMAGE: 'Visual Studio 2017', ADDRMDL: 64, TOOLSET: 'msvc-14.1' }
     - { APPVEYOR_BUILD_WORKER_IMAGE: 'Visual Studio 2015', ADDRMDL: 64, TOOLSET: 'msvc-14.0' }
-    - { APPVEYOR_BUILD_WORKER_IMAGE: 'Visual Studio 2015', ADDRMDL: 64, TOOLSET: 'msvc-12.0' }
-    - { APPVEYOR_BUILD_WORKER_IMAGE: 'Visual Studio 2015', ADDRMDL: 32, TOOLSET: 'msvc-11.0' }
-    - { APPVEYOR_BUILD_WORKER_IMAGE: 'Visual Studio 2015', ADDRMDL: 32, TOOLSET: 'msvc-10.0' }
 
 cache:
   - '%USERPROFILE%\clcache'