* Adds the ability to have a thread efficient long poll service (such as the eventqueue)

* If this doesn't melt the Http Server, this will significantly reduce the number of threads in use on regions with many users.
* Adds AddPollServiceHTTPHandler, and RemovePollServiceHTTPHandler to BaseHttpServer
* Generic enough to be used for many long poll services, not only the EventQueue.

OpenSim/Framework/Servers/Tests/OSHttpTests.cs

@@ -67,6 +67,7 @@ namespace OpenSim.Framework.Servers.Tests
             public void Send(byte[] buffer) {}
             public void Send(byte[] buffer, int offset, int size) {}
             public void Respond(string httpVersion, HttpStatusCode statusCode, string reason, string body, string contentType) {}
+            public void Close() { }
 
             public event EventHandler<DisconnectedEventArgs> Disconnected = delegate { };
             /// <summary>