Film buffs are, by nature, always looking for the next hot thing in moviegoing, but sometimes, even the devotees need a push to begin looking seriously at unfamiliar work. So goes the thinking behind the Toronto International Film Festival’s “Planet Africa” project, which has recently been retired after ten years of specifically promoting African films at the fest. The idea is not to create a one-time celebration of underappreciated cultures, but to bring those cultures permanently onto the North American radar screen by making them a valued part of the festival.