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/global/constants.c

@@ -102,9 +102,6 @@ double people_damage = 1.00;	/* Civs/mil/uw take this fraction of damage */
 double collateral_dam = 0.10;	/* Side effect damage to sector */
 double assault_penalty = 0.50;	/* attack factor for para & assault troops */
 
-/* opt_FUEL */
-int fuel_mult = 10;		/* 1 fuel = 10 mob */
-
 float land_grow_scale = 2.0;	/* how fast eff grows for land units (xETUS) */
 float ship_grow_scale = 3.0;	/* how fast eff grows for ships (xETUS) */
 float plane_grow_scale = 2.0;	/* how fast eff grows for planes (xETUS) */