This is a bit of a mess. LibreSSL portable puts the LibreSSL version number in the pc files. In-tree LibreSSL uses 1.0.0 which is clearly wrong--using SHLIB_VERSION_NUMBER for the version makes absolutely no sense to me. The pc files used by OpenSSL also use the release version. The simplest thing would be for us to use the LibreSSL version too.
For third-party code that uses "pkg-config --atleast-version=foo", it might be more useful to list what version of OpenSSL we are "compatible" with but I don't think that is really workable since there is no one-to-one comparison. My preference would be to just extract the version from LIBRESSL_VERSION_TEXT in opensslv.h. - todd
