Windows: add combase to the WinSDK.core module

Ensure that this header properly gets modularized into its own module.

Author: compnerd

stdlib/public/Platform/winsdk.modulemap

@@ -27,6 +27,11 @@ module WinSDK [system] {
       export *
     }
 
+    module com {
+      header "combaseapi.h"
+      export *
+    }
+
     module compress {
       header "compressapi.h"
       export *