***Low-budget knockoff of “Jack the Giant Slayer” is original enough to stand on its own*** The Asylum’s “Jack the Giant Killer” (2013) isn’t a remake of the 1962 film, but rather a mockbuster for which the company is known. These kinds of movies are produced with the intention of exploiting the mass publicity machine of a blockbuster with a similar title or subject, in this case “Jack the Giant Slayer,” which was released to theaters around the same time. While both films feature a main character named Jack and massive beanstalks that lead up to an amazing realm above the clouds, they’re...