[PowerPC64] Adds ABI flags to 'file' magic

[alfredo]

Summary

The distinction between ELF header version and OpenPOWER ELF ABI version is confusing for most of people, so this adds text to "file" output to make it clear about which OpenPOWER ELF ABI version binary was built for.

The strings used in this change are based on "64-Bit ELF V2 ABI Specification/3.1. ELF Header" document available at http://openpowerfoundation.org/wp-content/uploads/resources/leabi/content/dbdoclet.50655241_97607.html

Example:

$ file t1-Flag2 -m -m contrib/file/magic/Magdir/elf
t1-Flag2: ELF 64-bit MSB executable, 64-bit PowerPC or cisco 7500, OpenPOWER ELF V2 ABI, version 1 (FreeBSD), dynamically linked, interpreter /libexec/ld-elf.so.1, for FreeBSD 13.0 (1300033), FreeBSD-style, not stripped

Test Plan

Output with different Flags:

Flags 0x0, Machine 0x15:

t1-Flag0:               ELF 64-bit MSB executable, 64-bit PowerPC or cisco 7500, Unspecified or Power ELF V1 ABI, version 1 (FreeBSD), dynamically linked, interpreter /libexec/ld-elf.so.1, for FreeBSD 13.0 (1300033), FreeBSD-style, not stripped

Flags 0x1, Machine 0x15:

t1-Flag1:               ELF 64-bit MSB executable, 64-bit PowerPC or cisco 7500, Power ELF V1 ABI, version 1 (FreeBSD), dynamically linked, interpreter /libexec/ld-elf.so.1, for FreeBSD 13.0 (1300033), FreeBSD-style, not stripped

Flags 0x2, Machine 0x15:

t1-Flag2:               ELF 64-bit MSB executable, 64-bit PowerPC or cisco 7500, OpenPOWER ELF V2 ABI, version 1 (FreeBSD), dynamically linked, interpreter /libexec/ld-elf.so.1, for FreeBSD 13.0 (1300033), FreeBSD-style, not stripped

Flags 0x2, Machine 0x2:

t1-Flag2-machine-SPARC: ELF 64-bit MSB executable, SPARC, version 1 (FreeBSD), dynamically linked, interpreter /libexec/ld-elf.so.1, for FreeBSD 13.0 (1300033), FreeBSD-style, not stripped

[luporl]

Looks good.