seed mode fixes

git-svn-id: http://libtorrent.googlecode.com/svn@9789 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda
merged and extended seed_mode fix from trunk

git-svn-id: http://libtorrent.googlecode.com/svn@9790 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda
fix test_recheck

git-svn-id: http://libtorrent.googlecode.com/svn@9791 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda