Don't store land unit stats in struct lndstr, part 2

Don't store land unit stats in struct lndstr, part 2

struct lndstr members lnd_spy, lnd_rad, lnd_ammo, lnd_fuelc,
lnd_fuelu, lnd_maxlight, lnd_maxlight are mere copies of struct
lchrstr members l_spy, l_rad, l_ammo, l_fuelc, l_fuelu, l_nxlight,
l_nland.  Remove them.

Make land unit selectors spy, rmax, ammo, fuelc, fuelu, maxlight
virtual.