Blender Git Loki

More optimization: Allocate all LinkNode need for loops in one step, instead of doing one alloc per loop.

This allocate a bit more memory than needed (since we won't use linknodes of 'sharp' loops),
but avoids calling BLI_linklist_prepend_memarena() once per 'smooth' loop.

Note: gave much less benefits than expected, in the end - guess memarena allocation is *really* fast!