[RFC] iconvdata/, localedata/: Fix TSCII and document tests.

[Florian Weimer]

* Carlos O'Donell via Libc-alpha:

> diff --git a/localedata/charmaps/TSCII b/localedata/charmaps/TSCII
> index 9646f326cb..3d9ae1fb5e 100644
> --- a/localedata/charmaps/TSCII
> +++ b/localedata/charmaps/TSCII
> @@ -2,8 +2,26 @@
>  <comment_char> %
>  <escape_char> /
>  <mb_cur_min> 1
> -<mb_cur_max> 1
> -% based on TSCII version 1.7
> +<mb_cur_max> 3
> +
> +% Tamil Script Code for Information Interchange
> +%
> +% Based on TSCII version 1.7
> +%
> +% The lower 128 code points are ASCII, but the upper code points are
> +% TSCII characters that often map to multiple Unicode code points.  The
> +% one-to-many mapping means that much of the character map is commented
> +% out since we don't support many-to-one mappings in POSIX-compatible
> +% character maps.  There are 179 such mappings where one encoded TSCII
> +% character is mapped to more than one Unicode code point.
> +%
> +% Note that iconv is capable of and supports such conversions, but iconv
> +% when run with character maps as from-encoding or to-encoding is unable
> +% to support such conversions.
> +%
> +% For conversion reference:
> +% https://www.unicode.org/notes/tn15/Tscii2Unicode2.pdf

Does this mean that after this change, glibc will no longer perform
proper multi-byte to wide string conversion for single-byte characters
such as 0x8c?  Or is the charmap file just for reference purposes, and
conversion of 0x8c to U+0B95 U+0BCD U+0BB7 U+0BCD works as before?

Thanks,
Florian