A HashMap in actionscript that can use arbitrary objects as keys.

Internally, three different things may be done for storage:
- Simple keys can utilize the Dictionary class, we just use one of those
  inside the map.
- If the key implements Hashable, we can hash it.
- Otherwise, use mx.utils.ObjectUtil to generate a hash for any other key and
  also to compare the keys. Keys are then wrapped in a KeyWrapper object
  that implements Hashable. This last case will also handle null as a key.


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4117 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/util/Hashable.as

@@ -0,0 +1,11 @@
+package com.threerings.util {
+
+public interface Hashable extends Equalable
+{
+    /**
+     * Get a hashcode for this Equalable object so that it may be placed
+     * in a HashMap.
+     */
+    function hashCode () :int;
+}
+}