2018 copyright date update

src/dring/media_const.h

src/dring/presence_const.h

src/dring/presencemanager_interface.h

src/dring/security_const.h

src/dring/videomanager_interface.h

src/enumclass_utils.h

src/fileutils.cpp

src/fileutils.h

src/ftp_server.cpp

src/ftp_server.h

src/generic_io.h

src/hooks/urlhook.cpp

src/hooks/urlhook.h

src/ice_socket.h

src/ice_transport.cpp

src/ice_transport.h

src/im/instant_messaging.cpp

src/im/instant_messaging.h

src/im/message_engine.cpp

src/im/message_engine.h