[Zucchini] Create elf types and utils.

Creates types and utility class to manipulate ELF header format and relocation
references.

BufferView: :modify() was also added.
Change-Id: Iacec212a2fb2f8a6c85d551eed4b8e0a84926d89
Reviewed-on: https://chromium-review.googlesource.com/1136846
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578034}
9 files changed