Remove CI builds not using C++11

Also add MSVS 2019 and 2022 builds to AppVeyor.

.github/workflows/ci.yml

@@ -71,7 +71,7 @@ jobs:
             use_xvfb: true
           - name: Ubuntu 18.04 wxGTK 3 STL
             runner: ubuntu-18.04
-            configure_flags: --enable-cxx11 --enable-stl --disable-compat30
+            configure_flags: --enable-stl --disable-compat30
             use_xvfb: true
           - name: Ubuntu 18.04 wxGTK 3 with clang
             runner: ubuntu-18.04

.github/workflows/ci_cmake.yml

@@ -63,7 +63,6 @@ jobs:
           - name: macOS 11 wxOSX
             runner: macos-11
             cmake_generator: Xcode
-            cmake_defines: -DCMAKE_CXX_STANDARD=11
           - name: macOS 11 wxIOS
             runner: macos-11
             cmake_generator: Xcode