Fix wxDataFormat comparison operators for wxDF_HTML under wxMSW.

This format is special as it doesn't have a fixed value and is registered
dynamically instead. So we need to call HtmlFormatFixup(), which checks if the
given custom format is actually wxDF_HTML, before comparing formats to ensure
that the real value assigned to this format compares correctly to the fixed
wxDF_HTML value.

Closes #15280.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74997 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/testableframe.cpp

@@ -18,6 +18,7 @@
 
 wxTestableFrame::wxTestableFrame() : wxFrame(NULL, wxID_ANY, "Test Frame")
 {
+    Move(2000, 200);
 }
 
 void wxTestableFrame::OnEvent(wxEvent& evt)