Blender Git Loki

Cleanup: use BKE_fcurve_ prefix for keyframing bezier functions

- BKE_bezt_subdivide_handles -> BKE_fcurve_bezt_subdivide_handles
- binarysearch_bezt_index -> BKE_fcurve_bezt_binarysearch_index

These functions are specific to F-Curves and don't make sense for other
uses of BezTriple (curve-object data for e.g.)

Also:

- Move detailed doxygen comment above code, following code-style.
- Mark bezt_add_to_cfra_elem unused.