Merge branch 'ab/attribute-format'

Many "printf"-like helper functions we have have been annotated with __attribute__() to catch placeholder/parameter mismatches. * ab/attribute-format: advice.h: add missing __attribute__((format)) & fix usage *.h: add a few missing __attribute__((format)) *.c static functions: add missing __attribute__((format)) sequencer.c: move static function to avoid forward decl *.c static functions: don't forward-declare __attribute__