Fix generation of native instance constructors in C++ generator.

Author: tritao

src/Generator/Generators/C/CppSources.cs

@@ -292,9 +292,12 @@ public virtual void GenerateClassConstructor(Class @class)
 
             var nativeType = $"::{@class.QualifiedOriginalName}*";
             WriteLine($"{nativeType} {ClassCtorInstanceParamIdentifier})");
+            GenerateClassConstructorBase(@class);
 
             WriteOpenBraceAndIndent();
 
+            WriteLine($"{Helpers.InstanceIdentifier} = {ClassCtorInstanceParamIdentifier};");
+
             UnindentAndWriteCloseBrace();
             NewLine();
         }