This reports the current status on a single line every second, mirroring
similar functionality in GNU dd, and carefully interacts with SIGINFO.
PR: 229615
r337865:
dd: Incorporate some changes from imp for status=progress
Notable changes from what landed in r337505:
- sigalarm handler isn't setup unless we're actually using it
- Humanized versions of the amount of data transferred in the progress
update
r337869:
dd(1): Kill off duplicate progress definition following r337865