Add Chrome Frame support. Close requests in web.py.

- Add meta tag to vnc.html and vnc_auto.html so that if Chrome Frame
  is installed, it is used.

- Add detection to default_controls.js that shows a message with
  a Chrome Frame install link if the user is using a version of IE
  without Canvas support.

- Fix web.py so that requests have their connection closed after they
  are completed.  This has been a bug for a while but it prevents
  Chrome Frame from working because Chrome Frame doesn't activate
  until the initial request connection closes.

utils/web.py

@@ -17,6 +17,7 @@ import SimpleHTTPServer as server  # python 2.X
 def do_request(connstream, from_addr):
     x = object()
     server.SimpleHTTPRequestHandler(connstream, from_addr, x)
+    connstream.close()
 
 def serve():
     bindsocket = socket.socket()