A rewriting of the elfdump utility

Hi there,

This patch is a rewriting of elfdump utility using the libelf library.
Major improvements include:

* Support for extended numbering.
* Support for symbol hash table dump.

It also fixes several bugs of the old elfdump when handling 64bit ELF
binary.

Test I've done:

1. make universe
2. apply both the old elfdump and the new one to the
   huge amount of ".o" and executables produced by the
   "make universe" and compare the results.

The patch has been reviewed by jkoshy_at_ and I think it may be
time for a public review.

(patch against /usr/src/usr.bin/elfdump in -CURRENT)

Thank you!

Best Regards,
Kai Wang