Adding the following characters will enable support for several Lakota Sioux orthographies:
LATIN CAPITAL LETTER H WITH CARON (U+021E)
LATIN SMALL LETTER H WITH CARON (U+021F)
LATIN CAPITAL LETTER H WITH DOT ABOVE (U+1E22)
LATIN SMALL LETTER H WITH DOT ABOVE (U+1E23)

Text samples can be found on the languagegeek site:
http://www.languagegeek.com/siouan/lakotastory.html