hg: kulla/dev/langtools: Per discussions, an update replacing a variable resets it to null. User always warned.

[robert.field at oracle.com]

Changeset: 5dc343ff762c
Author:    rfield
Date:      2015-02-07 20:19 -0800
URL:       http://hg.openjdk.java.net/kulla/dev/langtools/rev/5dc343ff762c

Per discussions, an update replacing a variable resets it to null.  User always warned.

! repl/src/tool/Repl.java