"nonidentical" means "the input character index is valid, but not
corresponding to the output codeset."
"ilseq" means "the input character index is invalid for the input codeset."
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)