Big5 "mostly" complete

[Rich Felker <dalias@aerifal.cx>]

Hi all,

I just committed a revision to iconv Big5 support, adding current
standardized extensions up to nearly the maximum possible level. The
whatwg definition of Big5 is still a bit bigger, so maybe we should
research whether its additions make sense to support. There would be
no size or performance cost to supporting them, since they just fill
in holes in the table without extending the table size.

I'm still unclear on what, if any, action needs to be taken for
extended Taiwan variants of Big5. In theory UAO could be added (minus
the PUA mappings) but it's quite large and I still don't feel like I
have a good understanding of whether there are users who need it.
Whatwg has no mention of it with encoding standards
(http://encoding.spec.whatwg.org/) and only Mozilla seems to support
it. If it's needed in Taiwant for representing native-language text in
a Big5-based encoding, that's a strong argument for supporting it
anyway, but if it's just for representing mixed-language text (as a
poor substitute for Unicode) I feel like it would be hard to justify
including it, and maybe we could think about later supporting it as a
local nonstandard encoding via charmap files...

Comments?

Rich