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Nodes Splines: Apply tilt to normal evaluation

This patch makes the spline tilts (interpolated to the evaluated points)
affect the evaluated normals, allowing manual control of the rotation of
each profile in the curve to mesh node.

The method is based on Animation Nodes code, which keeps the data in
direction vector form, and rotates around the tangent vector.

Differential Revision: https://developer.blender.org/D11152