add deprecation for old anchor command options

src/main/java/com/denizenscript/denizencore/utilities/Deprecations.java

@@ -152,6 +152,10 @@ public class Deprecations {
     // Prime candidate for functionality removal - was never recommended.
     public static Warning notableItems = new SlowWarning("Using the note command with items is deprecated: this has never been recommended and is more likely to introduce bugs than ever do anything useful.");
 
+    // In Bukkit impl, Added 2020/03/08
+    // Prime candidate for functionality removal - has not been recommended for many years.
+    public static Warning anchorWalk = new SlowWarning("Using the anchor 'walkto'/'walknear' options is deprecated: use the walk command with the npc.anchor tag instead, and 'assume' should be replaced by the teleport command.");
+
     // ==================== SPECIAL deprecations: Minecraft version ====================
 
     // In Bukit impl, To be removed when Minecraft 1.12.2 is no longer supported by the Bukkit impl: