websockets: Initial websocket support. * 8sync/contrib/base64.scm: * 8sync/contrib/sha-1.scm: * 8sync/ports.scm: * 8sync/systems/websocket.scm: * 8sync/systems/websocket/client.scm: * 8sync/systems/websocket/frame.scm: * 8sync/systems/websocket/server.scm: * 8sync/systems/websocket/utils.scm: New files. * Makefile.am (SOURCES): Add them. * 8sync/systems/web.scm (<web-server>): Rename upgrade slot to upgrade-paths and use it. (.upgrade-paths, maybe-upgrade-request): New variables. (web-server-client-loop): Upgrade protocol if appropriate.