Update for upcoming VS R60

A number of deprecated functions have been removed, including get_plugins which is used here: https://github.com/Infiziert90/getnative/blob/master/getnative/utils.py#L22.

Upstream commit: https://github.com/vapoursynth/vapoursynth/commit/d7884782b3d4dac8ebc210a66d14a94b3843ef54