R43 – Cleaning up the remaining mess from R41

R41 changed quite a few things internally and that created regressions. New zimg branch, added alpha support and a pile of changes behind the scenes in the python module caused problems. The release fixes several zimg bugs, a vspipe hang on error, vsscript functions not being threadsafe and a few more things.

Possibly (un)breaking changes:

  • get_output() in python only returns a tuple when alpha is set, this more or less restores the previous behavior