Description

Functions are currently deprecated by documentation.

Nobody reads that.

C23 has __deprecated__, we should use that everywhere, maybe even CI-test for Doxygen-deprecation without C-deprecation, and verify that at least some compiler complains loudly when a deprecated function is used.

This should help us make our deprecation process more trustworthy.

Next steps

• Add attribute everywhere
• Add defines to unbreak any compilers that don't like it.
• Check which compilers now give warnings / errors.