No longer you can utilize the free (and instant) labour of station
workers, transporting your cargo from one part of the station to
the other. No more!
Based on patch by dP.
(cherry picked from commit df400ef84a)
Over the years, things got reused and changed, making the current
names somewhat unclear in what they actually mean and do.
(cherry picked from commit 30172fc037)
Move them into a new GoodsEntryData struct referenced
using a std::unique_ptr from GoodsEntry.
The unique_ptr may be nullptr if the cargo list and flow stat map
are both empty (this is the case for unused cargoes).
This reduces GoodsEntry from 128 to 24 bytes,
and Station from 8680 to 2024 bytes,
(on Linux x86_64).
