s/ElfAddr/Elf_Addr/

[jmgurney]

In testing this on FreeBSD (aarch64 specifically), I ran across that I needed to change both ElfAddr and ElfOff to Elf_Addr and Elf_Off respectively in src/plt-elf.c to compile. Once I did, it compiled and pasted the tests.

This was on:
FreeBSD generic 13.0-CURRENT FreeBSD 13.0-CURRENT #25 r361402+b36207bba19d-c268811-dirty: Sat May 30 08:17:13 UTC 2020 vagrant@freebsd:/usr/obj/home/vagrant/freebsd/arm64.aarch64/sys/GENERIC arm64

I'm not sure what is the best way to address this change/difference w/o impacting other OSes.

[lbmeng]

On Linux with musl C, this should be:

s/ElfAddr/ElfW(Addr)
s/ElfOff/ElfW(Off)