Fix JIS X 0201 decode [nkf-bug#30162]

patched by deton.
http://sourceforge.jp/ticket/browse.php?group_id=248&tid=30162
Support JIS X 0213.

patched by deton. [nkf-bug#30167]
http://sourceforge.jp/ticket/browse.php?group_id=248&tid=30167
Suppress warnings on -ansi -Wextra
Returning flags are nkf_char
Remove extra outputs [ruby-dev:47057]

https://bugs.ruby-lang.org/issues/7892
Remove CVS Id