Don't send unnecessary events when wxSpinCtrlDouble loses focus

Only send the event when the control loses focus if its value has really
changed.

Closes https://github.com/wxWidgets/wxWidgets/pull/436

src/generic/spinctlg.cpp

@@ -410,7 +410,7 @@ void wxSpinCtrlGenericBase::OnSpinButton(wxSpinEvent& event)
 
 void wxSpinCtrlGenericBase::OnTextLostFocus(wxFocusEvent& event)
 {
-    SyncSpinToText(SendEvent_Text);
+    if ( SyncSpinToText(SendEvent_Text) )
         DoSendEvent();
 
     event.Skip();