Fix build with newer compilers

Index: source/libs/paragui/include/pgwidget.h
--- source/libs/paragui/include/pgwidget.h.orig
+++ source/libs/paragui/include/pgwidget.h
@@ -269,7 +269,7 @@ class DECLSPEC PG_Widget : public PG_MessageObject, pu
 	Return the widgetid
 	@return	id of the widget
 	*/
-	int GetID();
+	unsigned int GetID();
 
 	/**
 	Find a child that is identified by the given ID.
