Some .o files need to be rebuilt if config.h changes. Adding it to the
list of headers may still fail to solve the problem, because some of
the Makefiles use implicit rules or do not list dependencies properly.
In all games, rs_write_room_reference() stored -1 for a nonexistent
room, but rs_read_room_reference() did not check for out-of-bounds
values, leading to pointers to rooms[-1], which sometimes caused
crashes. rs_read_room_reference() has now been modified to use NULL
instead.
Some of the games required further changes to replace NULL with the
pointer to the actual room. Others are capable of handling NULL for
objects not in any room.
Super-Rogue, like Rogue V4, stored data of machine-dependent length in
the savefile, to prevent cheating. This made saved games non-portable.
Also deleted was a check that used this data, and prevented restoring
savefiles from backup.
This change BREAKS SAVEFILE COMPATIBILITY, but old files can be
converted by removing the block at offset 0x1e with length
sizeof(ino_t) + sizeof(dev_t) + 2 * sizeof(time_t). That seems to be
0x14 on i686 and 0x20 on x86_64.
