@OPTIMIZE: store non-zigzagged during the decode passes, and only de-zigzag when dequantizing

after we see SOS

returns number of contours

rects array must be big enough to accommodate all characters in the given ranges

note: this routine clips fills that extend off the edges... ideally this wouldn't happen, but it could happen if the truetype glyph bounding boxes are

since most people won't use this, find this table the first time it's needed