unsigned long dkim_ssl_version(void);
Retrieve the SSL version number against which the library was compiled.
||dkim_ssl_version() can be called at any time.
The constant OPENSSL_VERSION_NUMBER as defined by
the OpenSSL package.
- The value returned by this function has no meaning to the library.
The intent here is to confirm that the library and applications using
it were both compiled with compatible versions of OpenSSL.