Blender Git Loki

Cycles: Avoid over-allocation in decouple ray marching

It could have happened with really long rays and small steps.

Step size will be adjusted to the clamped number of steps in order
to preserve render result compatibility as much as possible.

We should probably reformulate this a bit, so it will give the
same looking results without step tweaks. But this new behavior
should already be much better that it was before.