bug#34663: remove ftx font backend

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Cc: rgm@gnu.org,  34663@debbugs.gnu.org
> Date: Thu, 02 Jan 2020 21:44:41 +0100
> 
> Now that the emacs-27 branch is cut, perhaps it is time to consider
> applying this to master?  I have attached a rebased patch.

Yes, but:

  . please add a NEWS entry about ftx's removal (in the "Installation
    Changes" section)
  . please add a NEWS entry on the emacs-27 branch saying that this
    font backend is deprecated and will be removed

Thanks.