- final cleanup of sectnum related stuff.

Made sure that remaining uses of sector indices are safe to be kept and deleted a few redundant functions.

source/core/gamefuncs.cpp

@@ -300,6 +300,21 @@ void checkRotatedWalls()
 	}
 }
 
+//==========================================================================
+//
+// check if two sectors share a wall connection
+//
+//==========================================================================
+
+bool sectorsConnected(int sect1, int sect2)
+{
+	for (auto& wal : wallsofsector(sect1))
+	{
+		if (wal.nextsector == sect2) return true;
+	}
+	return false;
+}
+
 //==========================================================================
 //
 // vector serializers