This addresses warnings from Clang-Tidy's `readability-else-after-return`
rule in the `source/blender/blenkernel` module. Not all warnings are
addressed in this commit.
No functional changes.
The files are now split up into the following sections:
- `BKE_anim_path.h` and `anim_path.c` for path/curve functions.
- `BKE_anim_visualization.h` and `anim_visualizationanim_path.c` for
animation visualization (mostly motion paths).
- `BKE_duplilist.h` for DupliList function declarations. These were
already implemented in `object_dupli.c`, so they were rather out of
place being declared in `BKE_anim.h` in the first place.
No functional changes.
