- combine nsICharsetConverterManager2 and nsICharsetConverterManager
- get rid of nsIAtom in most of the methods
- provide versions of getUnicodeDecoder/Encoder which don't do alias resolution
- change all charset types to ASCII strings
- clean up some other i18n APIs which could be simplified
- fix all consumers of all changed i18n interfaces
r=jshin, smontagu
rs=sfraser
fix bug 7964 : Add ISO-2022-KR decoder (to Unicode) for
Korean emails. Encoder is NOT included since ISO-2022-KR should
not be used for outgoing emails.