busybox

libbb: shrink wget/tftp progress indicator code a bit more

This makes size display 5-char wide instead of 6-char, but now it's smarter
(can show sizes in "12.3M" format).

function                                             old     new   delta
bb_progress_update                                   654     622     -32

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>