Replacement of charsetalias.properties file.

Dear Developers,

Could you tell me how the charset alias works now?

Let me give you some background why I wanted to know. Previously, I
have written a small utility that runs on Mac OS X which tinkers the
charsetalias.properties file a bit to handle many "big5-HKSCS" encoded
web sites that declared themselves incorrectly as "big5". It simply
replaces the target encoding of big5 with big5-HKSCS instead. As big5-
HKSCS is a superset of big5, it shows big5 encoded site correctly as
well as misconfigured big5-HKSCS sites. I have just downloaded Firefox
4.0 beta 7 and discovered that the charsetalias.properties file is no
longer there. Could you tell me how the charset handling works in
Gecko 2.0?

My little utility can be downloaded from here:
http://www.macupdate.com/info.php/id/19216/i-speak-cantonese