AIs test station catchment in reverse to how players see station catchment.
This did not take account of non-rectangular station catchment areas, so AIs
could end up placing stations in locations that did not accept/deliver cargo.
Display of industry production around tiles (as shown when placing a station)
did not take account of the station catchment changes, so still showed production
from an industry even if it was not covered by a tile.
This is fixed by making a set of nearby industries that are covered, instead of
looping over all possible industries.
