[Patch, AArch64, ILP32] 0/5 Add support for ILP32

[Yufeng Zhang]

Hi,

A set of five patches will be sent shortly as the binutils part of 
changes that add support for ILP32 in the AArch64 baremetal toolchain.

The five patches will be organized as the following:

1. Rename elf64-aarch64.c to elfnn-aarch64.c
2. Parametrize elfnn-aarch64.c and add basic support for ILP32 in ld and 
gas.
3. Add support for ELF32 relocs and refactor the handling of relocs in 
elfnn-aarch64.c.
4. Split elfnn-aarch64.c to elfxx-aarch64.c and refactor the handling of 
PLT.
5. Improve the debugging experience with the generated files.

Please note that the patches were split in a way to help the review; 
they need to be applied in order and only the full application of all 
patches can enable a successful build.

Patches for gcc and newlib changes will be sent later and the ABI 
documents will be made public soon.

Thanks,
Yufeng