Function Funnel for vctrans vapoursynth Plugin

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Funnel

The transition from Clip A to Clip B occurs as A frame is funnelled out in the opted direction, revealing B frame.

## trans.Funnel(clip, clipb clip[, float overlap = 1.0 ][, int dir = 1])

Parameter description:
clip : A clip. Constant format.
clipb : B clip. Must have identical format of A clip
overlap : transition time length in seconds. Floating point. Must correspond to at least 8 frames
dir : 1 to 4 corresponding to North, East, South and West
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