openssl: add blacklist-by-serial. This lets us blacklist certs by serial as well as by sha256 fingerprint, and adds the ability to comment in the blacklist file. TEST=script (added to package tests) BUG=chromium-os:20060 Change-Id: I57e98aa856a14d76341f41050d38477238649f37 Signed-off-by: Elly Jones <ellyjones@chromium.org>