Merge topic 'CM_OVERRIDE-clang'

3f77655d CM_OVERRIDE: fix feature test for clang

Source/Checks/cm_cxx_override.cxx

@@ -1,11 +1,13 @@
 struct Foo
 {
+  Foo() {}
   virtual ~Foo() {}
   virtual int test() const = 0;
 };
 
 struct Bar : Foo
 {
+  Bar() {}
   ~Bar() override {}
   int test() const override { return 0; }
 };