Support for x86_64 binary patching

[elfmaster]

Currently Shiva supports x86_64 for loading ELF micro-programs (See https://github.com/elfmaster/shiva) but does not support x86_64 microcode patching.

Support for x86_64 microcode patching will be easiest to implement since much of the x86_64 code is already done, we will need to adapt the Transform code into the x86_64 apply_relocation() work.

[elfmaster]

This port is almost done, see branch x86_64_port

[elfmaster]

Shiva now supports x86_64 patching. There is an x86_64_port branch that I've been working on. It's not yet merged into master