SI-7791 Line number table reflects underlying file

Since positions ultimately know their ultimate
positions in their ultimate source, use that line
number, ultimately, when emitting line number
table entries.

It is possible, but possibly not useful, to emit
both the actual (ultimate) line number and the
nominal one.

The `int`-valued line number of the `StackTraceElement`
is "derived" from the attribute.

note: working on clever way to test it.  Since REPL and scripter do the same thing, i.e., wrap some code, it ought to be easy to test them the same way.  The wrapping mechanism is quite different, but maybe this is an opportunity to reconsider that, under the aegis of replating.