fixed typo

git-svn-id: http://libtorrent.googlecode.com/svn@10415 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda
fix torrent_info constructor documentation

git-svn-id: http://libtorrent.googlecode.com/svn@10416 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda