roafteriniter: Add in the roafteriniter implementation

This commit adds in the roafteriniter plugin. Usage instructions can be
found in README.md.

BUG=chromium:860068
TEST=make test, make arm64_test, make ctest, make kern(4.14.y), make
kern(upstream)

Change-Id: If8d107f2820d656262831cf9f5b135118a02e260
Reviewed-on: https://chromium-review.googlesource.com/1244403
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Commit-Ready: Zubin Mithra <zsm@chromium.org>
Tested-by: Zubin Mithra <zsm@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
7 files changed