RFR 8182489: jshell tool: rerun multiline snippet from history corrupts history

[Robert Field]

Please review (for JDK 10) ---

Bug:

     https://bugs.openjdk.java.net/browse/JDK-8182489

Webrev jdk repo (code fix):

     http://cr.openjdk.java.net/~rfield/8182489v0jdk.webrev/

Webrev langtools repo (test):

     http://cr.openjdk.java.net/~rfield/8182489v0langtools.webrev/

Thanks,
Robert