clear ink from attr

[LCD]

SETATTR only for paper needs BAND function to work. I myself use pokes, especialy for the whole screen (768 bytes), but SATATTR is fast too. You will need ATTR to read the Attribute at given coordinate, then binary AND it with a mask (BIN 11000111) to get a value without paper. Then you can use a new paper if it is different than zero by binary OR-ing (BOR) it with Paper shifted to left 3 times ( newpaper<<3 ).