Let players stop/start units:

(genitem, lndstr, nukstr, plnstr, shpstr): New members off, lnd_off,
nuk_off, pln_off, shp_off.
(NSC_GENITEM): New selector off.
(land, nuke, plan, shi): Display efficiency prefixed by `=' when off.
(start, stop, player_coms): Rewrite, new syntax.  Print only objects
that actually change.
(start_hdr, stop_hdr, start_stop_hdr): Consolidate.
(item_u, start_stop, start_stop_sector, proff, start_stop_unit)
(start_stop_unit_hdr, unit_type_name): New.
(upd_land, upd_plane, planerepair, upd_ship): Obey and clear stoppage.

include/land.h

@@ -57,6 +57,7 @@ struct lndstr {
     signed char lnd_type;	/* index in lchr[] */
     signed char lnd_effic;	/* 0% to 100% */
     signed char lnd_mobil;	/* mobility units */
+    unsigned char lnd_off;	/* repairs stopped? */
     short lnd_tech;		/* tech level ship was built at */
     char lnd_army;		/* group membership */
     coord lnd_opx, lnd_opy;	/* Op sector coords */