RFR 8173845: JShell API: not patch compatible

[Robert Field]

Please review....

Bug:

     https://bugs.openjdk.java.net/browse/JDK-8173845

Webrev:

     http://cr.openjdk.java.net/~rfield/8173845v0.webrev/

Note: the additional test was the straw that broke the camels back -- I 
could not get the tests to run without running out of memory, so, for 
them to pass I had to add more memory clean-up.

Thanks,
Robert