Add a generifying factory method

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5334 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/util/StreamableHashMap.java

@@ -40,6 +40,14 @@ import com.threerings.io.Streamable;
 public class StreamableHashMap<K, V> extends HashMap<K, V>
     implements Streamable
 {
+    /**
+     * Creates an empty StreamableHashMap
+     */
+    public static <K, V> StreamableHashMap<K, V> newMap ()
+    {
+        return new StreamableHashMap<K, V>();
+    }
+
     /**
      * Constructs an empty hash map with the specified number of hash
      * buckets.