GetPhonebookIndex: Fix handling for minor Japanese kana characters

This adds minor Japanese kana character handling to meet the
unicode collation algorithm.

-Normalize digraphs (yori, koto) into first reading letter.
-Treat dakuten, dot, onbiki, iteration marks as a symbol.
-Add handling for minor small katakana letter.

Signed-off-by: Yutaro Ogasawara <yutaro.ogasawara@gmail.com>