hg: jdk/sandbox: 8196298: Add null Reader and Writer

[chris.hegarty at oracle.com]

Changeset: 1b3ee04e3e54
Author:    rriggs
Date:      2018-03-19 09:58 -0400
URL:       http://hg.openjdk.java.net/jdk/sandbox/rev/1b3ee04e3e54

8196298: Add null Reader and Writer
Reviewed-by: bpb, forax, smarks, alanb, rriggs
Contributed-by: patrick at reini.net

! src/java.base/share/classes/java/io/Reader.java
! src/java.base/share/classes/java/io/Writer.java
+ test/jdk/java/io/Reader/NullReader.java
+ test/jdk/java/io/Writer/NullWriter.java