DEFAULT_VERSIONS conflicts

[Roger Marquis]

Per the 20171214 UPDATING entry:

   Support for some deprecated variables is going to be removed soon. If
   you use any of the following constructs (usually in /etc/make.conf),
   you must switch to the new incantations:
   ...
   WITH_OPENSSL_BASE                  DEFAULT_VERSIONS+= ssl=base
   WITH_OPENSSL_PORT                  DEFAULT_VERSIONS+= ssl=port

Question is what occurrs when the port version is also specified:

   DEFAULT_VERSIONS+=ssl=libressl

Some builds report an error when both are specified depending on the
order of, for example:

   DEFAULT_VERSIONS+=ssl=libressl
   DEFAULT_VERSIONS+=ssl=port

Is there documentation on how to specify multiple port options?

Roger