[bug#44806] [PATCH staging 0/6] Add Pitivi

[Leo Prikler]

Hello Guix,

the following patch series adds the video editor Pitivi [1].  As it
depends on GStreamer >= 1.17.90 (i.e. de facto 1.18), it has to be
applied to the staging branch.  There are also some minor changes to
the packages around it, e.g. the now deprecated gst-transcoder and a
minor fix to ffmpeg-4.2 (for those who want to build pitivi without
waiting hours on Rust).

Regards, Leo. 

[1] http://www.pitivi.org/