clean headers inclusion, pass to good type at some variables

src/66/66-scandir.c

src/include/66/66.h

src/include/66/backup.h

src/lib66/backup_realpath_sym.c

src/lib66/db_switch_to.c

src/lib66/db_update.c

src/lib66/get_enum.c

src/lib66/rc_send.c

src/lib66/rc_unsupervise.c

src/lib66/scandir_send_signal.c

src/lib66/set_livedir.c

src/lib66/set_livescan.c

src/lib66/set_livestate.c

src/lib66/set_livetree.c

src/lib66/svc_init_pipe.c

src/lib66/svc_send.c

src/lib66/svc_switch_to.c

src/lib66/svc_unsupervise.c

src/lib66/tree_copy.c

src/lib66/tree_find_current.c