Can not set charset to GB18030

[jacknlliu]

Test on archlinux with locale set "en_US.UTF-8" and "zh_CN.gb18030".

When editing a text file, I want to change the charset to GB18030, but after I check the "GB18030" from Menu "Format"-->"Charset"-->"Open with charset.."--> .
And I press F5, but the bottom of the editor indicator not changed!
And the charset "GB18030" really not worked!