Support halfwidth katakana + voiced sound mark

Because NormalizerMySQLUnicodeCIExceptKanaCIKanaWithVoicedSoundMark is
not MySQL compatible normalizer.

MySQL compatible normalizers should behave same as MySQL. But the
normalizer is groonga original normalizer. We can change behavior if
there is reasonable reason.

https://gist.github.com/y-ken/eb49eaad879f47b27cec#comment-832107

Suggested by Y.Kentaro. Thanks!!!