OpenSSL exception as agreed, with new SPDX expression Licence text approved by co-contributor Mark Wooding in personal email. DPDX expression roughly following https://spdx.github.io/spdx-spec/v2.3/using-SPDX-short-identifiers-in-source-files/ which doesn't contemplate using LicenseRef for an exception, but I think the meaning is clear, and it is useful to do it this way. Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>