[Cin] zimg 2.8

[Andrea paz]

Thanks, with the two "exports" I compliled without any problems.
No message in console. Among the ffmpeg plugins, "zscale" appeared.
Applying it to an edit gives no error messages. But whatever changes I
try to make to any of its parameters I always get the same error:

PluginFVClient::process_buffer() F_zscale
  err: Generic error in an external library

Any advice on how to make it work? It would be a really nice plugin
that allows you to control every aspect of a transcode, from size to
colors.