* fhandler.h (enum change_state): Add.
(fhandler_base::status): Add a bit to has_changed flag.
(fhandler_base::has_changed): Implement with type change_state.
* fhandler.cc (fhandler_base::raw_write): Accomodate type change
of has_changed.
* fhandler_disk_file.cc )fhandler_disk_file::touch_ctime): Also
touch modification time if has_changed == data_changed.
(fhandler_disk_file::fchmod): Also open on 9x, otherwise we can't
touch ctime. Accomodate type change of has_changed.
(fhandler_disk_file::fchown): Accomodate type change of has_changed.
(fhandler_disk_file::facl): Ditto.
(fhandler_disk_file::ftruncate): Ditto.
(fhandler_disk_file::link): Ditto.
(fhandler_base::open_fs): Ditto.