Update to 12.3.0

Hi, this "update as usual" should resolve the following bugs:

• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1050972
• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1050970

upstream/pristine-tar branches are updated, I'd only tag debian/2%12.3.0-1 once we are happy and actually uploading.