The CodeQL autobuild has started failing the CodeQL CI workflow a few days ago, due to their doxygen not supporting the -q command line argument. This replaces the use of -q by redirecting stdout and stderr in the silent rules case. Fixes: https://github.com/gphoto/libgphoto2/issues/1046
Rules for the API docs:
1. DO NOT DOCUMENT ANYTHING YET
2. If you know a method to keep API docs and internal docs apart, with
doxygen, please tell us.
3. If this has been solved, start documenting the external interface.
Thank you.