simworld: wrap karte_t::step body with intr_disable/intr_enable

[janry]

INT_CHECK calls inside karte_t::step (during fab_list iteration in
simfab.cc, and several explicit INT_CHECK("...") sites in simworld.cc
itself) can pump GUI events while step is mid-iteration over
fab_list / convoi_array / cities. If a welt_gui_t ("New world")
dialog is open, its "Start" handler in gui/welt.cc calls
welt->init(), which runs karte_t::destroy() and frees the very
factory whose step is on the stack. ASAN reports a
heap-use-after-free in array_tpl<ware_production_t>::get_count.

The karte_t::interactive() loop calls step() with no wrap; only
modal_dialogue() in gui/simwin.cc currently guards the call with
intr_disable()/intr_enable(). Pushing the wrap into step() itself
makes the guard apply to every caller and renders the
modal_dialogue wrap redundant (harmless, can be removed in a
follow-up if desired).

[prissi]

Depending on map size, mouse movements without enough INT_CHECK can be very sloppy. The proper way is to do this interaction by a tool. Same needs to be done for loading/scenarios/ ....

I tried this with a very large map and it was dramatic, fps dripping to 2 while before still 7-10 were possible.

For the moment, I changed the list to numerical enumerators as ancient C which will somewhat cope with deleting factories etc. while iterating.

[janry]

something like this?

[prissi]

Something, the handling of the parameter could still be via pointers for the internal tools so heightmaps work without potentially crashing the current map when overwriting their settings during a step. I had started this already in the last commit, so thank for this, I will incorporate it.