Add NoPushWindowCheck compatibility flag

- For maps like xtheateriii that expect non-blocking push lines to
  activate when you are standing on them and run into a completely different
  line, there is now this compatiblity.txt-only flag.

src/compatibility.cpp

@@ -106,6 +106,7 @@ static FCompatOption Options[] =
 	{ "ignoreteleporttags",		BCOMPATF_BADTELEPORTERS, SLOT_BCOMPAT },
 	{ "rebuildnodes",			BCOMPATF_REBUILDNODES, SLOT_BCOMPAT },
 	{ "linkfrozenprops",		BCOMPATF_LINKFROZENPROPS, SLOT_BCOMPAT },
+	{ "disablepushwindowcheck",	BCOMPATF_NOWINDOWCHECK, SLOT_BCOMPAT },
 
 	// list copied from g_mapinfo.cpp
 	{ "shorttex",				COMPATF_SHORTTEX, SLOT_COMPAT },

src/doomdef.h

@@ -351,6 +351,7 @@ enum
 	BCOMPATF_BADPORTALS			= 1 << 4,	// Restores the old unstable portal behavior
 	BCOMPATF_REBUILDNODES		= 1 << 5,	// Force node rebuild
 	BCOMPATF_LINKFROZENPROPS	= 1 << 6,	// Clearing PROP_TOTALLYFROZEN or PROP_FROZEN also clears the other
+	BCOMPATF_NOWINDOWCHECK		= 1 << 7,	// Disable the window check in CheckForPushSpecial()
 };
 
 // phares 3/20/98:

src/p_map.cpp

@@ -1640,7 +1640,7 @@ static void CheckForPushSpecial (line_t *line, int side, AActor *mobj, bool wind
 {
 	if (line->special && !(mobj->flags6 & MF6_NOTRIGGER))
 	{
-		if (windowcheck && line->backsector != NULL)
+		if (windowcheck && !(ib_compatflags & BCOMPATF_NOWINDOWCHECK) && line->backsector != NULL)
 		{ // Make sure this line actually blocks us and is not a window
 		  // or similar construct we are standing inside of.
 			fixed_t fzt = line->frontsector->ceilingplane.ZatPoint(mobj->x, mobj->y);

wadsrc/static/compatibility.txt

@@ -376,3 +376,8 @@ D62DCA9EC226DE49108D5DD9271F7631 // Cheogsh 2 map04
 	setthingz 1648 528
 	setthingz 1649 528
 }
+
+B9DFF13207EACAC675C71D82624D0007 // XtheaterIII map01
+{
+	DisablePushWindowCheck
+}