RFR JDK-8187910: Charset MS950_HKSCS not supported in JDK 9

[Xueming Shen]

Hi

Please help review the change for JDK-8187910.

issue: https://bugs.openjdk.java.net/browse/JDK-8187910
webrev: http://cr.openjdk.java.net/~sherman/8187910/webrev

The change is to add charset MS950_HKSCS into sun.nio.cs/"standard 
charset provider"
on Windows platform. It appears it is being used for Windows7's 
Traditional, Hong Kong
S.A.R. locale, as reported.

Thanks,
Sherman