Potential bug: Time remaining gets reduced after pausing

[mlago16]

This seems like a bug. To reproduce it, just pause for a while and then continue. The remaining time value is reduced unexpectedly.

[Zenju]

This is a consequence of the latest changes in FFS 10.0 related to multithreading. When paused FFS will finish processing the active item in the background and only block when trying to get the next. This is the simplest and most efficient implementation regarding support for "pause". But it has the side effect of introducing a slight (?) and temporary distortion to the progress speed, since time is paused, but a bit of background work continues. The alternative would be to have each worker thread serialize with the main thread after each and every junk of work, which would probably be okay considering that the workload is I/O bound, but it still seems excessive.