gajim's license needs OpenSSL exception

Hi!

gajim is licensed under the GNU GPLv3+ and requires OpenSSL. Since OpenSSL's license is not compatible with the GNU GPLv3, it needs an exception to allow "linking" with it. ("linking" in quotes, because this is Python, but it basically is the same)

See https://swift.im/git/swift/tree/COPYING.gpl for an example:

Additional permission under GNU GPL version 3 section 7

If you modify this Program, or any covered work, by linking or combining
it with the OpenSSL library (or a modified version of that library), 
containing parts covered by the terms of the OpenSSL License, the 
licensors of this Program grant you additional permission to convey 
the resulting work.

OpenSSL is trying to move to the Apache 2.0 license (see https://www.openssl.org/blog/blog/2017/03/22/license/ and https://license.openssl.org/), and will then be compatible with GPLv3, but as this hasn't been completed yet, the current situation could cause problems.

Regards, Thomas