Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Move helper functions `_libelf_ar_get_{name,number,string}()` and
`_libelf_ar_open()` to a new compilation unit "libelf_ar_util.c"
to break the circular dependency between "elf_memory.o" and
"libelf_ar.o".

Obtained from: elftoolchain
MFC after: 1 month