W32: Add dummy prelight style to check/radio buttons to propagate prelight to check/radio marks

https://bugzilla.gnome.org/show_bug.cgi?id=727210

gtk/resources/theme/gtk-win32-base.css

@@ -152,6 +152,12 @@ GtkAssistant .sidebar .highlight {
 
 /* Check buttons */
 
+/* This is meaningless, it just enables prelight propagation to check/radio mark */
+GtkCheckButton:prelight,
+GtkRadioButton:prelight {
+  color: @fg_color;
+}
+
 .check {
     background-color: transparent;
     background-image: -gtk-win32-theme-part(button, 3 1);