ProgressBar::Inc() makes unnecessary calls to time::Instant::now

[A-Sand-of-Piecy-Ham]

It does not appear to be possible to increment the progress bar without a relatively slow system-call to get the time. This happens even when the progress bar does not require accessing the current time. For more often increments, these system-calls add up to a significant amount of time (granted this is for a very high number of increments).

Possibly there should be a way to increment the bar without causing a tick, or a separate bar that does not make calls to get the time and is only incremented manually (does not allow attaching timers).

[djc]

I guess we could have inc_no_draw() and a separate force_redraw() call? If you need a very high number of increments, perhaps you can accumulate locally and call inc() with a higher delta?