Fixed walkthrough blocker in Sin City 2 via compatibility entry

It was impossible to complete Sin City 2 The Satan Complex without cheating since ZDoom 2.6.0
Change in applying of DeHackEd patches from 77a4b9a29b broke triggering of important linedef that pushes friendly marine to exit switch

https://www.doomworld.com/idgames/levels/doom2/Ports/s-u/satanx

src/compatibility.cpp

@@ -51,6 +51,7 @@
 #include "textures.h"
 #include "g_levellocals.h"
 #include "vm.h"
+#include "actor.h"
 
 // MACROS ------------------------------------------------------------------
 
@@ -449,6 +450,13 @@ DEFINE_ACTION_FUNCTION(DLevelCompatibility, SetLineSectorRef)
 	return 0;
 }
 
+DEFINE_ACTION_FUNCTION(DLevelCompatibility, GetDefaultActor)
+{
+	PARAM_PROLOGUE;
+	PARAM_NAME(actorclass);
+	ACTION_RETURN_OBJECT(GetDefaultByName(actorclass));
+}
+
 
 //==========================================================================
 //