RFR 8143006: jshell tool: /edit doesn't process each line as same as inputs for jshell

[Robert Field]

Please review --

Bugs:

     jshell tool: /edit doesn't process each line as same as inputs for 
jshell
     https://bugs.openjdk.java.net/browse/JDK-8143006

     JShell tests: jdk/jshell/ExternalEditorTest.java -- unexpected 
results EditorTestBase.testEditClass1() and .testEditMethod1()
     https://bugs.openjdk.java.net/browse/JDK-8163816

Webrev:

     http://cr.openjdk.java.net/~rfield/8143006v0.webrev/

Thanks,
Robert