Don't send unnecessary events when wxSpinCtrlDouble loses focus

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

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

(cherry picked from commit 5e24bd162c)

src/generic/spinctlg.cpp

@@ -432,8 +432,8 @@ void wxSpinCtrlGenericBase::OnSpinButton(wxSpinEvent& event)
 
 void wxSpinCtrlGenericBase::OnTextLostFocus(wxFocusEvent& event)
 {
-    SyncSpinToText(SendEvent_Text);
-    DoSendEvent();
+    if ( SyncSpinToText(SendEvent_Text) )
+        DoSendEvent();
 
     event.Skip();
 }