improved seeding of files with small pieces to avoid swithing back and forth between unchoke sets
improved seeding of files with small pieces to avoid swithing back and forth between unchoke sets

git-svn-id: 6ed3528c1be4534134272ad6dd050eeaa1f628d3@2817 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda

svn2github/libtorrent-trunk,svn2github/libtorrent-trunk,svn2github/libtorrent-trunk,svn2github/libtorrent-trunk