playback.js: move to include/ for easier reference.

Easier to reference from web site (gh-pages branch).

tests/vnc_playback.html

@@ -38,7 +38,7 @@
     -->
 
     <script src="include/vnc.js"></script>
-    <script src="playback.js"></script>
+    <script src="include/playback.js"></script>
 
     <script>
         var fname, start_time;