Copy Java's valueOf factory method for primitive wrapper classes.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4217 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/util/Integer.as

@@ -13,6 +13,11 @@ public class Integer
 {
     public var value :int;
 
+    public static function valueOf (val :int) :Integer
+    {
+        return new Integer(val);
+    }
+
     public function Integer (value :int)
     {
         this.value = value;