Rip out XML-RPC server code for update_status 5.x-1.* clients

Now that update_status 5.x-2.0 is nearly out, and a 5.x-1.0 release of project* is imminent, we should probably rip out all the XML-RPC code in project_release.module that was added in HEAD. update_status 5.x-1.* should be dead, and we don't want this code in project* anymore. We *might* want to keep it (or a skeleton of it) around on d.o, just enough to tell the existing update_status 5.x-1.* users to upgrade, but that can be in a separate temporary module for d.o, instead of in project_release itself.