lenscorrection needs interpolation about frei0r

[ddennedy]

Here you can see it was intended by its author but never completed:
https://github.com/dyne/frei0r/blob/master/src/filter/lenscorrection/lenscorrection.c#L211

[pmjdebruijn]

Yeah I noticed that as well.

However, in the meantime I noticed defish0r too, which seems to be a good fit for my purposes, even though it technically doesn't support rectilinear lenses, it seemingly works well for mine.

defish0r also has choice of every common interpolator.

So adding proper rectilinear support to defish0r seems to make more sense now than adding interpolation to lenscorrection.