As this is now documented, it means 3rd party code can now directly make
use of these without having to reinvent the same logic, or worse,
rediscover the same driver bugs.
The compatibility.glsl file however stays private -- I don't expect
real-world projects needing *that much* diversity in their supported
GLSL versions, often the baseline is GLES 3.0 which makes a large part
of the file unnecessary, and the projects might choose to for example
always have implicitly queried uniform locations to not have to
maintain two code paths.
Vladimír Vondruš