Blender Git Loki

Disabled the child hair hull drawing feature.

This is incompatible with particle data structures in their current form.
Hull drawing requires sorting child particles based on the distance from
their primary parent. However, this changes the order of children, which
is the main method of generating random numbers for them. In the
viewport this is not a problem, but when rendering the children are
constantly recreated, using the respective deformed emitter mesh each
time. This leads to changing child orders when using the convex hull
sorting, and therefore different randomisation values.

To properly implement child hull drawing we would have to generate a
stable parent-child offset metric as well as avoiding any resorting in
the actual data arrays. This in turn requires terribly inefficient
drawing iteration, which could become a bottleneck by itself even before
taking cache coherence or OpenGL optimization requirements into account
(collecting child data into a dedicated buffer for drawing).