Adjust for the fact that the image info is now tracked by "struct elf_image".
(elf64_valid_object): Delete (it's now in elfxx.c.
(_UPTi_find_uwnind_table): Don't mmap the image here.
(get_unwind_info): Use tdep_get_elf_image() to obtain the ELF image.
(Logical change 1.45)