fixed GTK styles handling:

1. don't modify the style unless something changed
2. use gtk_widget_modify_style instead of gtk_widget_set_style, the latter is not recommended by GTK+ developers


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@27784 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/spinctrl.cpp

@@ -298,12 +298,6 @@ bool wxSpinCtrl::IsOwnGtkWindow( GdkWindow *window )
     return FALSE;
 }
 
-void wxSpinCtrl::ApplyWidgetStyle()
-{
-    SetWidgetStyle();
-    gtk_widget_set_style( m_widget, m_widgetStyle );
-}
-
 wxSize wxSpinCtrl::DoGetBestSize() const
 {
     wxSize ret( wxControl::DoGetBestSize() );