- add _citrus_stdenc_get_state_desc() interface to get
encoding-scheme-independent encoder/decoder state descriptions.
- make sure that iconv_std module uses it to judge whether the last
sequences forms complete shift sequences.
- bump minor of i18n_module because of get_state_desc().
add core engine of Citrus iconv and some support routines.
- iconv core (citrus_iconv)
- coded character set mapper (csmapper)
- encoding scheme database (esdb)
- standard encoding scheme handler (stdenc)
- basic character set manipulation utilities (bcs)
- mmap based infrastructure (citrus_lookup/_mmap/_memstream/_db)
- some source codes of new plugins (not built yet)