[9] RFR: 8145974: XMLStreamWriter produces invalid XML for surrogate pairs on OutputStreamWriter

[Aleks Efimov]

Hello,

Please, help to review the fix for XMLStreamWriter bug [1]:
XMLStreamWriter incorrectly writes surrogate pairs into pair of invalid 
character references.
For example: "\ud83d\ude0a" is transformed into "��". It 
should be one character reference "😊" instead.
The proposed patch fixes the XMLStreamWriterImpl to correctly process 
surrogate pairs:
http://cr.openjdk.java.net/~aefimov/8145974/9/00

The build with fix applied was tested with JTREG and JCK xml tests - no 
related issues detected.

Aleksej

[1] https://bugs.openjdk.java.net/browse/JDK-8145974