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/symbol.c

@@ -276,7 +276,6 @@ struct symbol ship_chr_flags[] = {
     {M_SUBT, "sub-torp"},
     {M_TRADE, "trade"},
     {M_SEMILAND, "semi-land"},
-    {M_OILER, "oiler"},
     {M_SUPPLY, "supply"},
     {M_CANAL, "canal"},
     {M_ANTIMISSILE, "anti-missile"},