* unexelf.c: Don't assume ElfW (Half) fits in int.

* unexelf.c: Don't assume ElfW (Half) fits in int.

(entry_address, find_section, unexec): Use ptrdiff_t, not int,
when dealing with ElfW (Half) values, since they can exceed 2**31
on 64-bit OpenBSD hosts.  Problem reported privately by Han Boetes.
(entry_address): Omit unused NUM arg.  All uses changed.