Listing the "Blender Foundation" as copyright holder implied the Blender
Foundation holds copyright to files which may include work from many
developers.
While keeping copyright on headers makes sense for isolated libraries,
Blender's own code may be refactored or moved between files in a way
that makes the per file copyright holders less meaningful.
Copyright references to the "Blender Foundation" have been replaced with
"Blender Authors", with the exception of `./extern/` since these this
contains libraries which are more isolated, any changed to license
headers there can be handled on a case-by-case basis.
Some directories in `./intern/` have also been excluded:
- `./intern/cycles/` it's own `AUTHORS` file is planned.
- `./intern/opensubdiv/`.
An "AUTHORS" file has been added, using the chromium projects authors
file as a template.
Design task: #110784
Ref !110783.
Also see #103343.
Couldn't move two files yet:
* `softbody.c`: The corresponding regression test fails. It seems like the
conversion to C++ changes floating point accuracy, but it's not clear where that happens exactly.
* `writeffmpeg.c`: Is a bit more complex to convert because of the static array in `av_err2str`.
Pull Request: https://projects.blender.org/blender/blender/pulls/110182
