* readline.scm: New module.
* boot-9.scm (repl-reader): New function.
(scm-style-repl): Call repl-reader, instead of doing the reading
ourselves. Remove repl-report-reset; it was never used for
anything.
(top-repl): If we've got the readline primitives, then redefine
repl-reader to use them.
If we've got the readline primitives, import the readline module.
