Load counters are redundant; they can be computed from the carrier
uids. Keeping them up-to-date as the carriers change is a pain, and
we never got that quite complete.
Computing load counters straight from the carrier uids every time we
need them would be rather inefficient, but computing them from cargo
lists is not. So do that.
Remove the load counters: struct shpstr members shp_nplane,
shp_nchoppers, shp_nxlight, shp_nland, and struct lndstr members
lnd_nxlight and lnd_nland.
Don't compute/update load counters in build_ship(), build_land(),
land(), ldump(), load_plane_ship(), load_land_ship(),
load_plane_land(), load_land_land(), lstat(), sdump(), shi(), sstat(),
tend_land(), check_trade(), put_combat(), pln_oneway_to_carrier_ok),
pln_newlanding(), fit_plane_on_ship(), fit_plane_on_land(),
unit_list().
Nothing left in fit_plane_off_ship(), fit_plane_off_land(), so remove
them.
load_land_ship(), load_land_land(), check_trade(), pln_newlanding(),
put_plane_on_ship(), take_plane_off_ship(), put_plane_on_land(),
take_plane_off_land() no longer change the carrier, so don't put it.
Remove functions to recompute the load counters from carrier uids:
count_units(), lnd_count_units(), count_planes(), count_land_planes(),
pln_fixup() and lnd_fixup(), along with the latter two's private
copies of fit_plane_on_ship() and fit_plane_on_land().
New cargo list functions to compute load counts: unit_cargo_count()
and unit_nplane(), with convenience wrappers shp_nplane(),
shp_nland(), lnd_nxlight(), lnd_nland().
Use them to make ship selectors nplane, nchoppers, nxlight, nland
virtual. They now reflect what is loaded, not how the load uses the
available slots. This makes a difference when x-light planes or
choppers use plane slots.
Use them to make land unit selectors nxlight and nland virtual.
Use them to get load counts in land(), ldump(), load_plane_ship(),
load_land_ship(), load_plane_land(), load_land_land(), sdump(), shi(),
tend_land(), fit_plane_on_land(), trade_desc(), unit_list().
Rewrite fit_plane_on_ship() and could_be_on_ship() to use
shp_nplane(). could_be_on_ship() now takes load count arguments, as
computed by shp_nplane(), so it can be used for checking against an
existing load as well.
Persistent game state encodes "who carries what" by storing the
carrier uid in the cargo. Cargo lists augment that: they store lists
of cargo for each carrier. They are not persistent.
New unit_cargo_init() to compute the cargo lists from game state.
Call it in ef_init_srv() and at the end of update_main().
New unit_onresize() to resize the cargo list data structure.
Installed as units' struct empfile callback onresize to make them
resize automatically with the unit files.
New unit_carrier_change() to update cargo lists when carriers change
in game state. Convenience wrappers pln_carrier_change(),
lnd_carrier_change() and nuk_carrier_change(). Call them from
prewrite callbacks to keep cargo lists in sync with game state.
To make that work, unused units must not point to a carrier. Add new
pln_oninit(), lnd_oninit() and nuk_oninit() take care of newly created
units. Change lnd_prewrite() and nuk_prewrite() to take dead land
units and nukes off their carrier. pln_prewrite() did that already.
New unit_cargo_first(), unit_cargo_next() to traverse cargo lists.
Convenience wrappers lnd_first_on_ship(), lnd_first_on_land(),
lnd_next_on_unit(), pln_first_on_ship(), pln_first_on_land(),
pln_next_on_unit() and nuk_on_plane(). The latter is disabled for now
because it clashes with an existing function.
land_unit as well.
(do_unit_move): Add view option for land units using unit_view().
Combine ship and land viewing using the unit_view().
(shp_view): Remove, not used any more, replaced by unit_view().
