Change: Use bitmap for free unit ID generation. (#12165)

This improves performance of finding the next free unit number for a vehicle.

Based loosely on pool's used slot bitmap.

Codechange: Don't scan vehicle pool to find targeting disaster vehicle when deleting any vehicle. (#12064)

* Codechange: Don't scan vehicle pool to find targeting disaster vehicle when deleting any vehicle.

When deleting a vehicle, the vehicle pool is scanned to find a targetting disaster vehicle. With lots of vehicles this can take some time, especially when deleting multiple consecutive vehicles.

Disasters vehicles can actually only target road vehicles. Store the DisasterVehicle index in the road vehicle, so that no pool scan is necessary.

* Change: Small UFOs no longer target a vehicle which is already a target.

Fix b0e73277: cargodist information got lost when splitting of cargo (#11280)

During b0e73277 we removed loaded_at_xy, but I kinda forgot that
it was a union with next_station. Now next_station wasn't copied
anymore, or checked in AreMergable.

Fix #10334: Store separate newgrf-safe version of date_of_last_service. (#11124)

This value is not changed when the date cheat is used, which caused issues with changing properties based on service date.

Co-authored-by: Peter Nelson <peter1138@openttd.org>

Codechange: automatic adding of _t to (u)int types, and WChar to char32_t

for i in `find src -type f|grep -v 3rdparty/fmt|grep -v 3rdparty/catch2|grep -v 3rdparty/opengl|grep -v stdafx.h`; do sed 's/uint16& /uint16 \&/g;s/int8\([ >*),;[]\)/int8_t\1/g;s/int16\([ >*),;[]\)/int16_t\1/g;s/int32\([ >*),;[]\)/int32_t\1/g;s/int64\([ >*),;[]\)/int64_t\1/g;s/ uint32(/ uint32_t(/g;s/_uint8_t/_uint8/;s/Uint8_t/Uint8/;s/ft_int64_t/ft_int64/g;s/uint64$/uint64_t/;s/WChar/char32_t/g;s/char32_t char32_t/char32_t WChar/' -i $i; done

Fix: Abort loading savegame if road vehicle is on invalid road type. (#10622)

This can happen if NewGRFs are missing so that engine or road type definitions are wrong.

Fix: check for the existence of shadow and rotor vehicles for aircraft

Instead of just assuming that it exists in the savegame that got loaded.

Feature: framework to make savegames self-descriptive

We won't be able to make it fully self-descriptive (looking at you
MAP-chunks), but anything else can. With this framework, we can
add headers for each chunk explaining how each chunk looks like
in detail.

They also will all be tables, making it a lot easier to read in
external tooling, and opening the way to consider a database
(like SQLite) to use as savegame format.

Lastly, with the headers in the savegame, you can freely add
fields without needing a savegame version bump; older versions
of OpenTTD will simply ignore the new field. This also means
we can remove all the SLE_CONDNULL, as they are irrelevant.

The next few commits will start using this framework.

Codechange: remove the special station/vehicle code from SaveLoad

With the new SLEG_STRUCT it is much easier to embed a struct
in a struct, where the sub-struct has limitations on when it is
being used.
This makes both the code easier to read (less magic) and avoids
the SaveLoad needing to know all these things about Stations
and Vehicles.

Codechange: rename SL_LST to SL_REFLIST to highlight the "reference" part

You can easily mistake SlList / SL_LST to be a list of SL_VAR, but
it is a list of SL_REF. With this rename, it hopefully saves a few
people from "wtf?" moments.

Codechange: Remove FOR_ALL_CHUNK_HANDLERS

Co-Authored-By: Patric Stout <truebrain@openttd.org>

Codechange: C++-ify lists for SaveLoad (#9323)

Basically, this changes "SaveLoad *" to either:
1) "SaveLoadTable" if a list of SaveLoads was meant
2) "SaveLoad &" if a single entry was meant

As added bonus, this removes SL_END / SLE_END / SLEG_END. This
also adds core/span.hpp, a "std::span"-lite.

Codechange: Convert saveload numbers to enum values.

(This was mostly achieved with a few in-place regexes)

Codechange: Remove value mangling and field misuse in SLE_WRITEBYTE.

The original translation functionality hasn't been used since 2007.

Change: Remove direction parameter from Vehicle::UpdateDeltaXY. (#6792)

The value is either unused or always the same as this->direction.

(svn r21933) -Codechange: Split cur_order_index into cur_auto_order_index and cur_real_order_index to keep track of the current real order in an unambiguous way.
-Fix [FS#4440]: Automatic orders behave now stable wrt. service orders and are not added or removed depending on the need of servicing.
-Fix: Various other issues with automatic orders, e.g. vehicles getting stuck with "no orders" when there are automatic orders at the end of the order list.