Fix ldd to work with more ELF files.

Fix ldd to work with more ELF files.

- Use libelf to parse ELF data structures and remove code duplication
  for ELF32.

- Don't require the OSABI field to be set to the FreeBSD OSABI for
  shared libraries.  Both AArch64 and RISC-V leave it set to "none"
  and instead depend on the ABI tag note.  For ldd, this means falling
  back to walking the notes in PT_NOTE segments to find the ABI tag
  note to determine if an ELF shared library without OSABI set in the
  header file is a FreeBSD shared library.

Approved by:	re (gjb)

(cherry picked from commit 9d4104b214963bb3371ada05cae8006940121634)
(cherry picked from commit fa3b2ad265d311191c1c8337bf3aa356f28480cb)