Add a feature to disable the Nagle algorithm on sockets in TCPServer

#5767: remove sgmlop support from xmlrpclib; the sgmlop parser does not do much validation and is no longer much faster than e.g. the cElementTree XMLParser.

This should also fix disconnect behavior cross-platform.

Fix O(n**2) performance problem in socket._fileobject

as both < and > than eachother.