Remove last MPLS chapter if less than 1 second from the end

Per our email conversation on 2013/02/03 and 2013/02/04:

> I've noticed that the last chapter in Blu-ray playlists is usually invalid; they're typically less than 1 second before the end of the movie, and they're not listed in the chapter booklet that comes with the disc.  For example, on disc 1 of "The Lord of the Rings: The Fellowship of the Ring" ([Amazon](http://www.amazon.com/The-Lord-Rings-Fellowship-Extended/dp/B0026L7H20)), 00100.mpls contains 28 chapters, but the chapter booklet only lists 27.  And the last chapter (01:45:43.128) is only 292 ms from the end of the disc (01:45:43.420), which makes it rather pointless.

This patch removes the last chapter in the MPLS file if it's less than 1 second before the end of the playlist.