This is for rendering the sprite properly in all areas the actor touches. The original thinglist is not sufficient for this and Boom's touching thinglist has other purposes and collects too much data.
This new list will only get filled in when the actor is actually crossing a portal plane, for the normal sector thinglist will still be used.
This piggybacks on the msecnode_t code which has been extended to be able to handle more than one list by passing the sector's membert pointers as parameters.
This required some changes to the Trace function because it turned out that the original was incapable of collecting the required information:
* actors are now also linked into blockmap blocks on both sides if they occupy the boundary of a sector portal.
* Trace will no longer set up parallel traces in all parts connected with sector portal, but only use one trace and relocate that on the actual boundary.
The only reason this even existed was that ZDoom's original VC projects used __fastcall. The CMake generated project do not, they stick to __cdecl.
Since no performance gain can be seen by using __fastcall the best course of action is to just remove all traces of it from the source and forget that it ever existed.
Sadly the mappers cannot be trusted to use a feature correctly. Despite repeatedly telling that portals on one-sided lines are problematic, everybody seems to do it this way - and then report bugs if it doesn't work. Under such circumstances the only safe option is to block such portals entirely.
See http://forum.zdoom.org/viewtopic.php?f=2&t=51511&p=898522#p898522 for a typical example of the problems this might cause.
This was accidentally deleted during one round of portal refactoring but is essential to prevent multiple teleport activations in one move.
Fixing this also allowed removing the fudging that was added to work around the issue in P_TryMove.
This could happen if the damage calculations resulted in a value between 0 and 1, which for the actual check was multiplied with the damage parameter of P_RadiusAttack which inflated the fractional value to something that looked like actual damage but was later truncated.
While testing this it became clear that with the higher precision of doubles it has to be avoided at all costs to compare an actor's z position with a value retrieved from ZatPoint to check if it is standing on a floor. There can be some minor variations, depending on what was done with this value. Added isAbove, isBelow and isAtZ checking methods to AActor which properly deal with the problem.
