[Gegl-developer] API change for samplers to pass inverse Jacobian data to samplers

[Nicolas Robidoux]

Because, AFAIK, representing transformations as 3x3 matrices is only
natural for affine, perspective and combinations, but not for more
general warps, it is my opinion that what should be passed to samplers
(so that those which may downsample use it) should either be an array
with four double entries or an object of a type which could be named
GeglMatrix2.

Is it really worth it to create (name) a new GEGL type just for this
purpose? A plain array sure seems more expedient.

Nicolas Robidoux