bpo-31333: Re-implement ABCMeta in C (#5273)

This adds C versions of methods used by ABCMeta that
improve performance of various ABC operations.
diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
index bf4131e..90330fa 100644
--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -228,6 +228,7 @@
     <ClInclude Include="$(zlibDir)\zutil.h" />
   </ItemGroup>
   <ItemGroup>
+    <ClCompile Include="..\Modules\_abc.c" />
     <ClCompile Include="..\Modules\_asynciomodule.c" />
     <ClCompile Include="..\Modules\_bisectmodule.c" />
     <ClCompile Include="..\Modules\_blake2\blake2module.c" />