dvd: add the last chapter

As suggested in issue #1251. I think the main point is that it acts as
a hack to return to the DVD menu when jumping past the last chapter,
because it will reach title-EOF, instead of explicitly jumping to the
next file (which usually exits the player).

This basically reverts commit 8b7418d, except it doesn't include an
off-by-1 error (apparently).

Closes #1251.