Merge branch 'ab/only-single-progress-at-once'

Further tweaks on progress API. * ab/only-single-progress-at-once: pack-bitmap-write.c: don't return without stop_progress() progress API: unify stop_progress{,_msg}(), fix trace2 bug progress.c: refactor stop_progress{,_msg}() to use helpers progress.c: use dereferenced "progress" variable, not "(*p_progress)" progress.h: format and be consistent with progress.c naming progress.c tests: test some invalid usage progress.c tests: make start/stop commands on stdin progress.c test helper: add missing braces leak tests: fix a memory leak in "test-progress" helper