Oh well, it’s a special character called an “okina”, which is usually just substituted in with an apostrophe.
http://en.wikipedia.org/wiki/Okina
Most of the time, Hawai’i is sufficient. There’s a trend that goes back for some time to include the okina, and also long marks (macrons) over long vowels. Since the Hawai’ian language only has twelve letters, a e h i k l m n o p u w, it’s more easily read by adding the okina in, and marking long vowels. (Plus, w has two sounds...) But it doesn’t matter, as Obama is about Hawai’ian as a Hawaiian Punch!
Oh, man... You've just destroyed one of my most cherished childhood beliefs! When did Hawaiian Punch get “de-certified?”