Various fixes related to the C++11/14 update (see issue #3140)

- Convert scoped_ptr to std::unique_ptr from <memory>
- Convert arraysize to base::size from include/base/cef_cxx17_backports.h
- Convert NULL to nullptr
- Include include/base/cef_callback.h instead of include/base/cef_bind.h
- Implicit conversion of CefRefPtr<T> or scoped_refptr<T> to T* is gone;
  use .get() instead

See the issue for additional details.

tests/cefclient/browser/window_test_runner_win.cc

@@ -65,7 +65,7 @@ void SetPosImpl(CefRefPtr<CefBrowser> browser,
     ::ShowWindow(root_hwnd, SW_RESTORE);
   } else {
     // Set the window position.
-    ::SetWindowPos(root_hwnd, NULL, window_rect.x, window_rect.y,
+    ::SetWindowPos(root_hwnd, nullptr, window_rect.x, window_rect.y,
                    window_rect.width, window_rect.height, SWP_NOZORDER);
   }
 }