fate: add test for the deshake video filter.

tests/lavfi-regression.sh

@@ -32,6 +32,7 @@ do_lavfi "crop"               "crop=iw-100:ih-100:100:100"
 do_lavfi "crop_scale"         "crop=iw-100:ih-100:100:100,scale=400:-1"
 do_lavfi "crop_scale_vflip"   "null,null,crop=iw-200:ih-200:200:200,crop=iw-20:ih-20:20:20,scale=200:200,scale=250:250,vflip,vflip,null,scale=200:200,crop=iw-100:ih-100:100:100,vflip,scale=200:200,null,vflip,crop=iw-100:ih-100:100:100,null"
 do_lavfi "crop_vflip"         "crop=iw-100:ih-100:100:100,vflip"
+do_lavfi "deshake"            "deshake"
 do_lavfi "null"               "null"
 do_lavfi "scale200"           "scale=200:200"
 do_lavfi "scale500"           "scale=500:500"

tests/ref/lavfi/deshake

+deshake             aa32fdc7f9f890dd62b0ea9c3ca16e60