Add some constants for waypoint priority

diff --git a/TomTomLite.lua b/TomTomLite.lua
index 8b088ac..f23f52a 100644
--- a/TomTomLite.lua
+++ b/TomTomLite.lua
@@ -64,6 +64,11 @@ function addon:Initialize()

     -- Events for world map overlays
     self:RegisterEvent("WORLD_MAP_UPDATE")
+
+    -- Set up some constants that can be used in other addons
+    self.PRI_ACTIVE = 15
+    self.PRI_NORMAL = 0
+    self.PRI_ALWAYS = math.huge
 end

 function addon:CreateCrazyArrow(name, parent)