Http-in and makes the host name for URL generation configurable.
Applied with changes:
llGetSimulatorHostname was not changed, because the change breaks
existing behavior and carries a data exposure risk. That value needs
to be configurable, the proposed fixed change is not acceptable.
* 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.