[13] RFR: Correct UnicodeDecoder U+FFFE handling

[naoto.sato at oracle.com]

Hello,

Please review the fix to the following issue:

https://bugs.openjdk.java.net/browse/JDK-8216140

The proposed changeset is located at:

http://cr.openjdk.java.net/~naoto/8216140/webrev.00/

This issue was previously discussed in 
https://bugs.openjdk.java.net/browse/JDK-8150449 and was closed as "not 
an issue" for JDK8. Unicode Consortium then made a corrigendum to 
Unicode 7 that recommends passing through of the code point. To conform 
to the standard, the offending test/error return has been removed, based 
on the recommendation in the previous consideration on 8150449.

Naoto