Doen't work with caucho resin Websocket

_From [mattermark3](https://code.google.com/u/112373130522707499621/) on December 12, 2013 08:26:48_

Description of the issue: Steps to reproduce: 1. Set up caucho resin
2. In servlet service add line:

final WebSocketServletRequest wsReq = (WebSocketServletRequest) req;
                
3. You get exception

WARNING: java.lang.ClassCastException: com.google.inject.servlet.ServletDefinition$2 cannot be cast to com.caucho.websocket.WebSocketServletRequest
java.lang.ClassCastException: com.google.inject.servlet.ServletDefinition$2 cannot be cast to com.caucho.websocket.WebSocketServletRequest

_Original issue: http://code.google.com/p/google-guice/issues/detail?id=792_