security/libressl: Add the possibility to build only libtls

[Franco Fichtner]

> On 21. Aug 2017, at 4:55 PM, Mathieu Arnold <mat at FreeBSD.org> wrote:
> 
>> Unless you build your own packages with OpenSSL from ports
>> you can just install LibreSSL and use it in your programs...
>> 
>> # pkg install libressl
>> 
>> OpenSSL lives in the base system, LibreSSL will be an optional
>> install under /usr/local.
> 
> 
> That is not quite true. As soon as you install openssl, openssl-devel,
> or libressl or libressl-devel, the ports framework will use it whenever
> you build something that needs SSL from the ports tree.

Maybe that wasn't clear.  I said "unless you build your own packages"
meaning "use prebuilt binary packages only".


Cheers,
Franco