vboot2: Add host library functions for signing to new struct format

Including signing with bare hashes, and signing an object with more
than one signature.  With unit tests, even.

BUG=chromium:423882
BRANCH=none
TEST=VBOOT2=1 make runtests

Change-Id: Iad0b9f9f6cca7129071aebf0cbc60c0daa94d382
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/231452
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
11 files changed