The twitch API shows this:
Code:
curl -H 'Accept: application/vnd.twitchtv.v2+json' -H 'Authorization: OAuth <access_token>' \
-d "channel[status]=Playing+cool+new+game!&channel[game]=Diablo" \
-X PUT https://api.twitch.tv/kraken/channels/test_user1

It is for java but you need to be the streamer name in mirc in order to do this so a differently named bot cannot make the name change unless the bot name is your twitch stream account