[TDF] Replace the circular buffer with a stack
[TDF] Replace the circular buffer with a stack

indeed there may be situations where two workers start processing
the same slot: there was no guarantee that the slot number which
was delivered by the circular buffer had not being assigned to
a worker which did not finish yet its work.

gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root