Compatibility between Version 3 and Version 2

UIPACK Version 3 is backwards compatible with Version 2 with the following exceptions:-

1. When using Text Viewports to display Menus, the original state (visible or hidden) of the Viewport will be restored following a call to use a Menu. Thus ``pop up" menus may be setup (provided the relative priorities of the Menu Viewport and other visible Viewports are setup correctly). If the Menu Viewport is to be kept visible, it should be displayed explicitly via a call to UI_DISPLAY_VIEWPORT prior to using any Menus.