The old code kept the dead thinker, resulting in constant deletion and recreation of the subsector links and PolyBSP because the interpolation kept running.
Changed it so that the thinker is destroyed and the polyobject gets blocked by setting a new flag.
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.
This check is only active for linedef based portals, due to the large amount of maps that did it wrong with thing based portals.
Although it may well be that there are some maps that abuse this omission for linedef portals as well, these are better handled with a compatibility option if the need arises.
The main reason this was added is to streamline and optimize the portal handling between renderers in ZDoom and GZDoom. For that both need to show the same general behavior and for linedef portals it is also important to handle the same as in Eternity.
In some situations it can happen that the sector here is not the frontsector of the anchor linedef, because some colinear node line with opposite direction causes this to be positioned on the wrong side. The only remedy here is to explicitly set the correct sector after spawning these things.
This isn't necessary. When rendering no actors from other groups may ever come into view directly - only when the respective part of the level is rendered through a portal. But at that point the camera is in a position where it's already correctly placed with relation to that actor.
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.
Added temporary solution for the same foreground and background colors of the title in OS X startup window
It's used in graphical startup screen, with Hexen style in particular (for example WolfenDoom - Blade of Agony)
Native OS X backend doesn't implement this yet
Due to the VC++ 2015 headers being rather bloated (the average include size per source is 400-500kb) this provides a noticable compile speedup, although right now this only covers the game code, so there should be more room for improvement.
