'get-or-insert-stream' is now the more generic 'get-or-insert' that can
handle tables of any value type. But callers have to be careful to cast
values to the right type.
Start of the final phase needed to implement SubX in SubX:
$ cat files.subx ... |dquotes |assort |pack |survey |hex > a.elf
survey.subx is responsible for assigning addresses to labels and segments.
