NULL usually terminates the strings; allowing to produce it via escape
sequences may lead to undefined behaviour.
- Make NULL escape sequences (e.g. `\0` and `\x0`) invalid.
- Add corresponding test.
- Introduce the new message: XKB_WARNING_INVALID_ESCAPE_SEQUENCE.
Usually it is better to use the corresponding human-friendly keysym
names. If there is none, then the keysym is most probably not
supported in the ecosystem. The only use case I see is similar to the
PUA in Unicode (see: https://en.wikipedia.org/wiki/Private_Use_Areas).
I am not aware of examples of this kind of use.
This tool checks whether messages codes are supported.
This is useful e.g. for CI, where one may want to grep for some XKB
error codes and ensure that these are still supported.
Pierre Le Marre