ean13composite: honour dontdraw (issue bwipp#54), with usematrix option

[gitlost]

Part-addresses issue https://github.com/bwipp/postscriptbarcode/issues/54 for ean13composite, adding new option usematrix (set if dontdraw set) that creates a pixs array containing the composite, separator and linear, the latter multiplied out by 72 rows. If dontdraw set returns pixs array, else renders with renmatrix. Text is not represented in the array.

See closed PR https://github.com/bwipp/postscriptbarcode/pull/194 for discussion.