Called when creating a new channel or changing the channel name in mod/settings.php
Hook data consists of an array
'name' => supplied name
If the hook handler determines the name is valid, do nothing. If there is an issue with the name,
set $hook_data['message'] to the message text which should be displayed to the member - and the name will
not be accepted.
if(mb_strlen($hook_data['name']) < 3)
$hook_data['message'] = t('Name too short.');