Beginnings of the ActionScript 3.0 client: checkpoint checkin.

There's a long way to go and I think I need to rethink the way streaming
will work, but this is a start. These classes all compile under
the flex environment.


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@3842 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/io/ArrayMask.as

@@ -0,0 +1,6 @@
+package com.threerings.io {
+
+public class ArrayMask
+{
+}
+}