new sid tune is bigger than 4k, so charset had to be moved
now (part of) first half of the charset actually is used by the sid
and ignored by the VIC; chars had to be redefined
loading colors was done in a dummy way by reading color of each tile
from the RLE array; but actually a tile always have the same color, then
this info is redundant; anyhow the character set had to be reshaped
properly in order to make easy infer the tile color from the tile value
