fix out-of-bounds access in elf.c:find_link

fix out-of-bounds access in elf.c:find_link

The out-of-bounds access is reproducible on 'ia64-strip' command
(see sample from https://bugs.gentoo.org/show_bug.cgi?id=622500)

The output file contains less section than original one.
This tricks 'hint' access to go out-of-bounds:

	* elf.c (find_link): Bounds check "hint".