Cleanup: Remove unused ChunkType flag CH_AUTO_LENGTH

CH_AUTO_LENGTH is no longer used anywhere, so remove all code
that depends on it.

Fix: next 67 savegame versions are used in PatchPacks; skip them (#8411)

Various of PatchPacks (Spring 2013, Joker, ChillPP) used versions
slightly higher than ours. Of course, as time went by, this
caught up with us, and we are now almost pushing a new version
that would conflict with them. To avoid users creating unneeded
issues about "why can I not load my savegame", lets be ahead of
the curve and flat-out refuse to load them.

Version-wise, this is totally fine. We have ~32k versions to go
before we run out (0x8000 is masked by JGRPP; we should avoid
using that). At the rate we bump savegames, this is not going to
happen in any sane reality.

Fix: do not add an offset to a nullptr

This is, by specs, undefined behaviour. See
https://reviews.llvm.org/D67122

In cases where this is done, optimizations done by LLVM can
generate code that causes crashes.

GetVariableAddress() had two (legit) ways this could happen:
- For SaveLoad set to global
- For SaveLoad set to SLE_VAR_NULL, where sld->address is always
a nullptr, and object could or could not be a nullptr.

Fix: Incorrect save/load array size of Town::cargo_accepted

In 11ab3c4e the number of cargo types was changed from 32 to 64.
The save/load of Town::cargo_accepted was not updated, such that
only half of the data structure is saved/loaded in savegame versions
199 to 218.
Discard and regenerate data from all savegame versions prior to 219.

Feature: Configurable game ending year

Functionally reverts 683b65ee1

Change: Limit memory allocations for each Squirrel instance

This can avoid out-of-memory situations due to single scripts using up the entire address space.
Instead, scripts that go above the maximum are killed.
The maximum is default 1 GB per script, but can be configured by a setting.

Feature: Industries with neutral stations (e.g. Oil Rig) only supply/accept cargo to/from their neutral station. (#7234)

This change is a controlled by a game setting, located under Environment ->
Industries which allows toggling the behaviour. It defaults to enabled.

"Company stations can serve industries with attached neutral stations"

When enabled, industries with attached neutral station (such as Oil Rigs) may
also be served by company-owned stations built nearby. This is the traditional
behaviour.

When disabled, these industries may only be served by their neutral station.
Any nearby company-owned stations won't be able to serve them, nor will the
neutral station serve anything else other than the industry.

Add: Option for population-linear town cargo generation

Introduce a new default algorithm for town cargo generation (passengers and mail), and a game setting to choose between the new and original algorithm.

The original town cargo generation algorithm has the property of the generated amount relating to the square of each building's population, meaning large towns easily produce more cargo than can realistically be transported. The problem is excessive cargo is amplified if playing with cargodist.

The new algorithm introduced instead has a linear relation to the population. The result is that smaller towns will produce slightly more cargo, while the largest towns will produce about a fourth of what they would with the original algorithm.

Existing savegames will use the original algorithm, while new games will default to the new algorithm.

Fix #6803: CargoMonitorID bit packing updated to handle 64 cargo types.

This requires a saveload bump to change the bitpacking on loading older saves.

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.

(svn r16909) -Fix [FS#2996]: NewGRF stations would be triggering assertions all over the place when using the more advanced station types.
-Change: make (rail) waypoints sub classes of 'base stations', make buoys waypoints and unify code between them where possible.

(svn r16338) -Codechange: split loading of references to two phases
In the first phase, indexes are stored. In the second phase, indexes are checked for validity and converted to pointers