Add code/logic to mask the last 8x8 sample before non 8x8
Add code/logic to mask the last 8x8 sample before non 8x8

The last sample before a transition seems to not-infrequently have
nonsense header 3 values.  Add code to read all of the image sizes in
the interval, find the last 8x8 samples before 4x4 or 6x6, and mark
them bad.

sot/mica,sot/mica