comms/qsstv: update to 9.5.8

Now builds and runs with current hamlib.

Changelog: http://users.telenet.be/on4qz/qsstv/manual/changelog.html

DOCS option removed since building it continues to be problematic,
and the upstream author encourages using the online documentation
anyway.

Approved by: arrowd (mentor)
Differential Revision: https://reviews.freebsd.org/D33313