- add simplified chinese welcome page

- add .zh-cn extension for zh-CN language code to default config.

Submitted by: kajaa <kajaa@eastday.com>
Reviewed by: <yinglichina@sina.com>


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@100075 13f79535-47bb-0310-9956-ffa450edef68