For some reasons the save_threshold_spin_button and bg_threads spin buttons
are linked to each other, which means both values are linked. I'm not sure
how this happened, and I don't think my patch introduced this, since I just
did a textual change from the previous save_threshold setting into the new
I can't see anything wrong from a cursory inspection of core_prefs.c and
.xml, but my GTK+ fu is weak.