Generate delegates to multifile class members in package facade classes

(unless using -Xmultifile-package-facades option)

compiler/serialization/src/org/jetbrains/kotlin/serialization/DescriptorSerializer.java

@@ -437,6 +437,15 @@ public class DescriptorSerializer {
         return packageProto(fragments, null);
     }
 
+    @NotNull
+    public ProtoBuf.Package.Builder packageProtoWithoutDescriptors() {
+        ProtoBuf.Package.Builder builder = ProtoBuf.Package.newBuilder();
+
+        extension.serializePackage(Collections.<PackageFragmentDescriptor>emptyList(), builder, stringTable);
+
+        return builder;
+    }
+
     @NotNull
     public ProtoBuf.Package.Builder packageProto(@NotNull Collection<PackageFragmentDescriptor> fragments, @Nullable Function1<DeclarationDescriptor, Boolean> skip) {
         ProtoBuf.Package.Builder builder = ProtoBuf.Package.newBuilder();