When GLSL sources were first included in Blender they were treated as
data (like blend files) and had no license header.
Since then GLSL has been used for more sophisticated features
(EEVEE & real-time compositing)
where it makes sense to include licensing information.
Add SPDX copyright headers to *.glsl files, matching headers used for
C/C++, also include GLSL files in the license checking script.
As leading C-comments are now stripped,
added binary size of comments is no longer a concern.
Ref !111247
These are meant to provide easy shape and AABB operation for culling.
They are currently incomplete but can be extended as one see fits.
The `common_debug_shape_lib.glsl` contains helper to draw thoses shapes.
