add option to smooth out wow brightness compensation

[eshaz]

• Adds --wow_adjust_smoothing_lines which allows the brightness adjustment for wow to be smoothed out. This fixes the horizontal brightness striping that occurs on noisy tapes, especially EP.
  • This can be set to --wow_adjust_smoothing_lines 0 to disable the smoothing and use the original wow brightness compensation.
  • Defaults to --wow_adjust_smoothing_lines 6 so that brightness adjustment is averaged over a rolling window of 6 lines

ld-decode changes added here: happycube#1014

https://imgsli.com/NDQ3MjQx

--wow_adjust_smoothing_lines 6 (new default)

• brightness bars are no longer visible, since the wow calculation is being smoothed to remove noise

--wow_adjust_smoothing_lines 0 (i.e. behavior before this fix)

• brightness bars show up since wow calculation is noisy due to noisy video

[oyvindln]

Seems good, may want to add it for cvbs-decode as well

[eshaz]

Seems good, may want to add it for cvbs-decode as well

Done. I made the default 0 since I'm not sure if the wow adjustment caused problems with cvbs, so it should work as-is by default.