Passing to tr using the "pick and discard" technique is more straight-
forwardly correct and less error-prone. It also allows users to
select their own character sets to be passed to tr.

I like being able to specify command line options (like -c) at the end
of the line (which is usually when I think of the fact that I need
them).

The attached patch uses getopt(1) to regularize the option list so that
lazy people like me can specify the options in any order.