Merge master to soc-2019-cycles-procedural.

Avoid writing to input variables and using reserved function names.

Previously, we edited the input variables directly, OSL doesn't like that. Moreover, we used the name `noise`, which is already a built-in function, so we changed the function names to `noise_texture_*` instead.

Remove magic numbers and swizzling from Noise code.

Previously, we used a random swizzling pattern as a sort of seed for noise, this proved bad in a lot of cases, including the cases where some of the components are constants. Additionally, we also added some offsets from a set of "magic numbers" as a form of seed. Those magic numbers are bad practice, so we introduced some new functions to generate random offsets based on the hash functions we already have, this happens at compile time, so this has no effect on performance.

Reconfigure the outputs of the Noise node.

We changed the order of outputs so that the Value output is first. We did that because users mostly use the first output, and since noise is most commonly used as a bump texture, roughness textures, or to control other non-color data, it make sense that the first output should be the Value one. Previously, most users used the Color output for practically everything just because it is first in the output list. So reordering should save users some render time without them realizing.

Refactor and clean up White Noise node.

Refactor and clean ip hashing code.

Fix Mapping node backward compatibility. Update inputs and properties.

Fix Mapping node backward compatibility. Update socket names.

Revert accidental renamming from previouse commit.

Refactor and clean up Mapping node.

Refactor and clean up Map Range node.

Refactor and clean up Clamp node.

Establish a naming convention in the versioning code.

Each individual versioning action should be a function of the signature: update_{NodeName}_*(ntree).

Revert "Restructure versioning code to avoid duplicate iterations. Pre-linking."

This reverts commit eae462bc89a59ec24e114ea0012ea6cda0defa0c. The previouse structure
was more readable and clear since every function edits the node tree individually.

Restructure versioning code to avoid duplicate iterations. Pre-linking.

Cleanup: Use more explicit names.

Merge remote-tracking branch 'origin/master' into soc-2019-cycles-procedural

Added Fraction operator to Vector Math node.

Add Ceiling operator to Vector Math node.

Add Floor operator to Vector Math node.