Introduce a wrapper for unrar code

This CL provides an interface for extracting RAR archives without
leaking the unrar symbols into Chromium. Note that the unrar_wrapper.h
still includes rar.hpp for the moment, until the old method of RAR
inspection is fully deprecated.

Bug: 934372
Change-Id: I585de272e7b91b9892a6f738309b2179a4f9af9b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1521982
Commit-Queue: Daniel Rubery <drubery@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Varun Khaneja <vakh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642203}
5 files changed