Generate wxWindowCreateEvent when creating windows in wxQt

Send the expected event at the very end of window creation process.

Closes https://github.com/wxWidgets/wxWidgets/pull/1119

src/qt/window.cpp

@@ -287,6 +287,9 @@ void wxWindowQt::PostCreation(bool generic)
     SetForegroundColour(wxColour(GetHandle()->palette().foreground().color()));
 
     GetHandle()->setFont( wxWindowBase::GetFont().GetHandle() );
+
+    wxWindowCreateEvent event(this);
+    HandleWindowEvent(event);
 }
 
 void wxWindowQt::AddChild( wxWindowBase *child )