Check for moderators and see if they have access to the board.
What it does:
- sets up the $board_info array for current board information.
- if cache is enabled, the $board_info array is stored in cache.
- redirects to appropriate post if only message id is requested.
- is only used when inside a topic or board.
- determines the local moderators for the board.
- adds group id 3 if the user is a local moderator for the board they are in.
- prevents access if user is not in proper group nor a local moderator of the board.