Fix: Gain socket is not available in ridged multifractal.

The gain socket in the Musgrave node should be available in the ridged
multifractal mode. The logic for the availability was incorrect.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D5989

Fix: Clamping in Map Range node works incorrectly.

The clamp option in the Map Range node doesn't work correctly when the
inputs are linked. The code didn't put that into considration.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D5987

Fix T69989: Correct Mapping node min/max versioning.

The old min/max options specified the target min/max values, they didn't
act as min/max operators. So the versioning code should be adjusted
accordingly.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D5828

Shading: Add Vertex Color node.

This patch adds a new Vertex Color node. The node also returns the alpha
of the vertex color layer as an output.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D5767

Shading: Add More Features To The Voronoi Node.

This patch allows the Voronoi node to operate in 1D, 2D, and 4D space.
It also adds a Randomness input to control the randomness of the texture.
Additionally, it adds three new modes of operation:

- Smooth F1: A smooth version of F1 Voronoi with no discontinuities.
- Distance To Edge: Returns the distance to the edges of the cells.
- N-Sphere Radius: Returns the radius of the n-sphere inscribed in
the cells. In other words, it is half the distance between the
closest feature point and the feature point closest to it.

And it removes the following three modes of operation:

- F3.
- F4.
- Cracks.

The Distance metric is now called Euclidean, and it computes the actual
euclidean distance as opposed to the old method of computing the squared
euclidean distance.

This breaks backward compatibility in many ways, including the base case.

Reviewers: brecht, JacquesLucke

Differential Revision: https://developer.blender.org/D5743

Shading: Extend Musgrave node to other dimensions.

This patch extends Musgrave noise to operate in 1D, 2D, 3D, and 4D
space. The Color output was also removed because it was identical
to the Fac output.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D5566

Fix: Rename the dimensions property in Noise nodes.

The `dimensions` property of the noise nodes has been renamed to
`noise_dimensions` because it conflicted with and overwrote the
`dimensions` property of the base node.

Reviewers: brecht, JacquesLucke

Differential Revision: https://developer.blender.org/D5705

Fix: Compile error due to undefined isinf function.

Some implementations of the standard c++ library doesn't define its
functions in the global namespace. So the `isinf` function might
fail in some systems. To fix this, we use the `ensure_finite`
function instead.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D5687

Fix T69532: Wave texture fails with a compile error.

`noise_turbulence` was renamed to `fractal_noise`.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D5691

Cycles: Ignore links with unavailable sockets.

Ignore links with unavailable/disabled sockets during shader graph
generation.