one more iconv alias

[Bruno Haible <haible at ilog dot fr>]

Hello,

In glibc-2.1.1, the iconvdata/gconv-modules file knows about EUC-CN, but
not about GB2312. But these are the same, according to the IANA character
set registry:

    Name: GB2312  (preferred MIME name)
    MIBenum: 2025
    Source: Chinese for People's Republic of China (PRC) mixed one byte,
            two byte set:
              20-7E = one byte ASCII
              A1-FE = two byte PRC Kanji
            See GB 2312-80
            PCL Symbol Set Id: 18C
    Alias: csGB2312

The fix would be to add "GB2312" and "csGB2312" as aliases for "EUC-CN" in
iconvdata/gconv-modules.

Note that GB2312 as a coded character set (CCS) is a 94x94 character set and
does not include ASCII. But as a character encoding scheme (CES) it is
the same as EUC-CN. We already have this distinction for Big5 (for which
glibc's iconv implements the CES including ASCII) and GBK (for which Solaris
iconv implements the CES including ASCII).

Bruno