Allow number of items per line to vary when pretty printing.

[schwerdf]

Currently, the pretty-printing methods responsible for printing lists of grammar symbols for Copper's error messages [1] have the caller specify a fixed number of items per line.

This should be changed to allow the caller to specify the maximum number of characters per line, as well as whether the items must be specified in order, allowing the number of items per line to vary and an optimal use made of space.