Improve slice browsing performance from 10fps to 90fps
Problem: On Intel i7 computers with NVidia GPUs, slice browsing was very slow (10-15fps).
Analysis: If "Threaded optimization" option in NVidia settings was disabled (by default it is enabled) then frame rate went up to 60fps (limited by vsync) to 89fps (without vsync).
Solution: Force image reslicing & mapping filters to use a single thread. It makes slice browsing fast (60-90fps) without disabling "Threaded optimization".