Drop all support for animation data from Blender versions 2.49 and
older.
- The `IPO` DNA struct is deleted, as is the `IDType_ID_IP` type
definition.
- Versioning code has been removed in its entirety.
- Loading a pre-2.50 blend file will issue a warning, stating that any
animation data that was there is now lost, and that the file should
be loaded & re-saved with Blender 4.5 to properly port the data.
Note that versioning of Action assignments (as in, picking a slot)
still uses the tagging + updating all tagged assignments as a
post-processing step. This is necessary because picking the right slot
is only possible after all Actions (also those from libraries) have
been versioned. We might be able to address this as well, by upgrading
legacy → slotted Actions "on the fly" versioning these Action
assignments. If we do that, I think that would be better in a separate
PR though, as it could introduce issues by itself.
Ref: #134219
Pull Request: https://projects.blender.org/blender/blender/pulls/145188
6bf8685628