Inventory letters are based on "identifiers" stored in objects' o_ident
field. Identifiers are allocated by get_ident(), which keeps a list of
objects that have them, to avoid giving the same identifier to multiple
objects.
The list is not stored in the savefile, so after restore, get_ident()
was not aware of existing identifiers. This resulted in picked-up
objects having the same inventory letters as objects restored from the
file.
The restore code now adds all objects with identifiers to the list.
The functions for restoring saved games failed to properly correct the
t_chasee pointer of monsters chasing the player. Such monsters would
attempt to chase NULL instead, with predictable results.
The r_flags field in struct room was being written as an int and read
as a short. This caused the restore functions to receive the wrong
data, usually an impossible string length, and abort.
This breaks save compatibility, though the save files had problems
anyway: the r_fires field should have been used, instead of reading and
writing r_flags twice.
