Re: Registration of new charset CP50220

[Masatoshi Kimura <VYV03354@nifty.ne.jp>]

The purpose of this registration is to "standardize" how to handle
errors when Web browsers encount illegal ISO-2022-JP sequences.
Mozilla encoder has changed a halfwidth katakana handling to match
the behavior.
https://bugzilla.mozilla.org/show_bug.cgi?id=563283

 > Decoding is identical (which might be most interesting for users
 > of tagged content).
The fist version of the registration had included all decoding methods 
which is supported by CP50220. (i.e. ESC ( J, SI, and 8bit)
However latter two methods were removed from the registration by two 
reasons.

1. Some implementation (e.g. Mozilla's one) don't support them.
Should Mozilla decoder be changed to match the begavior?

2. The charset supposed to be a 7-bit. It's strange to include a 8-bit 
character handling.
Changing the regstration to 8-bit is not a solution because it will 
require the Content-Transfer-Encoding MIME header field. It is not 
compatible with ISO-2022-JP. Old Microsoft Internet Mail/News had the bug.