fix file_progress

git-svn-id: http://libtorrent.googlecode.com/svn@10480 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda
store a copy of the info-hash in the torrent object to allow direct access to it from multiple threads

git-svn-id: http://libtorrent.googlecode.com/svn@10481 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda