Fix the APIv4 stubs

[Ichunjo]

Here's the beginning of the fixes. I would like to have to have some thoughts about some things:

• MessageType as enum?
• Add _writelines
• Add some comments for the deprecated methods
• add_log_handler should return a LogHandle object. For me it returns a NoneType when I tried. Should we add a new class for it?
• remove_log_handler isn't typed

This PR will fix #156

[Ichunjo]

APIV4 introduced VideoFormat instead of Format but there isn’t an AudioFormat? All the format properties are already stored in the AudioNode https://github.com/vapoursynth/vapoursynth/blob/master/src/cython/vapoursynth.pyx#L1924

[myrsloik]

APIV4 introduced VideoFormat instead of Format but there isn’t an AudioFormat? All the format properties are already stored in the AudioNode https://github.com/vapoursynth/vapoursynth/blob/master/src/cython/vapoursynth.pyx#L1924

Right, I forgot to make a separate AudioFormat object. I should probably do that. https://github.com/vapoursynth/vapoursynth/issues/776

[myrsloik]

Implemented the dir thing. Now you'll just have to distinguish between the bound audio/video cases and this can make some more progress.

[myrsloik]

Actually now I remember why I didn't make AudioFormat a separate class. Unlike the VSVideoFormat struct that can be serialized into a small int audio is more complicated. It's also relatively few values so it's easier to not lump it up as function arguments.

[myrsloik]

Are we getting closer to something that's mildly working?

[Ichunjo]

Fixing the return type has to be in the cython side. See my PR https://github.com/vapoursynth/vapoursynth/pull/783

[Ichunjo]

I finally did it!

[myrsloik]

Looks reasonable I guess. Not an expert on typing stuff