<i18n dev> [15] RFR: 8242010: Upgrade IANA Language Subtag Registry to Version 2020-04-01

[naoto.sato at oracle.com]

Hello,

Please review the fix to the following issue:

https://bugs.openjdk.java.net/browse/JDK-8242010

The proposed changeset is located at:

https://cr.openjdk.java.net/~naoto/8242010/webrev.00/

Besides the upgrade of the data file, I fixed the issue where 
EquivMapsGenerator had been ignoring "extlang" tag. Now it correctly 
maps the extlang, such as "zh-cmn" to its preferred language (in this 
case, "cmn") tag.

Naoto