libwt: cursor and Net support

libwt provides a high level c++ way of working with the SDL infrastructure. The latest update, available in SVN only, implements custom cursor support and wraps up the SDL_net functionality via the excellent library Net2 (http://www.gameprogrammer.com/net2/net2-1.html). libwt provides name resolution, TCP server sockets, TCP client sockets and UDP sockets.