Some modifiers used `MOD_deform_mesh_eval_get` to make sure they had
a mesh to retrieve vertex groups from. But since curves don't support
vertex groups anyway, and since the curve to mesh conversion is handled
by the (legacy) curve object modifier stack anyway, this is confusing
and unnecessary. This shouldn't give any behavior changes, but some
deform modifiers on legacy curve objects might be faster if they used
to do the conversion.
A lot of files were missing copyright field in the header and
the Blender Foundation contributed to them in a sense of bug
fixing and general maintenance.
This change makes it explicit that those files are at least
partially copyrighted by the Blender Foundation.
Note that this does not make it so the Blender Foundation is
the only holder of the copyright in those files, and developers
who do not have a signed contract with the foundation still
hold the copyright as well.
Another aspect of this change is using SPDX format for the
header. We already used it for the license specification,
and now we state it for the copyright as well, following the
FAQ:
https://reuse.software/faq/
