bug#26588: Add some (non-free?) font licenses.

[Clément Lassieur]

The first patch adds Bitstream Vera license, which IMHO is non-free.
Feel free to discuss it though, I'm not sure of the comment I wrote.

The font could be added even though it is non-free because it could be
considered a "Non-fonctional data".  See
https://www.gnu.org/distros/free-system-distribution-guidelines.html#non-functional-data.

The second patch adds Arev license, which is almost like Bitsteam Vera,
and is needed by 0ad-data (which I'm working on).

The third patch fixes font-bitstream-vera, which IMHO erroneously had
X11-style license.