Remove option FUEL

The abstract idea of tying ships and land units to a logistical tether
is sound, the concrete implementation as option FUEL is flawed.  It
adds too much busy-work to the game to be enjoyable.  It hasn't been
enabled in a public game for years.  The code implementing it is ugly,
repetitive, and a burden to maintain.

Remove selector fuel from ship_ca[] and land_ca[], and selectors
fuelc, fuelu from mchr_ca[] and lchr_ca[].  Remove fields fuelc, fuelu
from ship.config and land.config.

Remove command fuel from player_coms[].

Deprecate edit key 'B' in doship(), dounit(), and don't show it in
pr_ship(), pr_land().

Drop opt_FUEL code from build_ship(), shi(), sdump(), ship_damage(),
show_ship_stats(), do_mob_ship(), nav_ship(), build_land(), land(),
ldump(), land_damage(), show_land_stats(), do_mob_land(),
resupply_all(), resupply_commod(), get_minimum(), has_supply(),
unit_list(), vers().

Remove opt_FUEL, fuel_mult, struct shpstr member shp_fuel, struct
mchrstr members m_fuelc and m_fuelu, M_OILER, struct lndstr member
lnd_fuel, struct lchrstr members l_fuelc and l_fuelu, fuel(), and
auto_fuel_ship().

src/lib/commands/vers.c

@@ -162,9 +162,6 @@ vers(void)
         pr("The starting mobility when acquiring a sector or unit is %d.\n",
 	   -(etu_per_update / sect_mob_neg_factor));
     pr("\n");
-    if (opt_FUEL)
-	pr("For ships and land units, fuelu makes %d mobility.\n\n",
-	   fuel_mult);
     pr("Ships on autonavigation may use %i cargo holds per ship.\n", TMAX);
     if (opt_TRADESHIPS) {
 	pr("Trade-ships that go at least %d sectors get a return of %.1f%% per sector.\n",