[metapost] mpost interactive prompt

[Nicola]

Hello,
for some time I have been wondering whether it would be
possible to improve mpost's command line interface by adding
readline functionality. For those who are not familiar with
such libraries, that means, for example, using arrows to
browse through older commands, using ctrl keys to jump to
the start/end of the line, etc…

Is there any legacy requirement that would prevent such
enhancements?

Nicola