This replaces header include guards with `#pragma once`.
A couple of include guards are not removed yet (e.g. `__RNA_TYPES_H__`),
because they are used in other places.
This patch has been generated by P1561 followed by `make format`.
Differential Revision: https://developer.blender.org/D8466
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.
