As many open source projects have started doing it, we're removing the
current year from the copyright notice, so that we don't need to bump
it every year.
It seems like only the first year of publication is technically
relevant for copyright notices, and even that seems to be something
that many companies stopped listing altogether (in a version controlled
codebase, the commits are a much better source of date of publication
than a hardcoded copyright statement).
We also now list Godot Engine contributors first as we're collectively
the current maintainers of the project, and we clarify that the
"exclusive" copyright of the co-founders covers the timespan before
opensourcing (their further contributions are included as part of Godot
Engine contributors).
Also fixed "cf." Frenchism - it's meant as "refer to / see".
GLAD 1 creates unusable loaders for EGL, while the newly released GLAD 2
does not, so for consistency I thought that it would be a good idea to
uniform things beforehand. While it had some API changes some renames
were all that was needed and everything works like before, at least on
the Wayland branch.
I've kept the structure identical, although this new generator has quite
a few hefty features, such as a single header mode.
I've also added GLAD to `thirdparty/README.md`, but I haven't specified
that in the commit title because it's a very small "fix".
