expose use_disk_cache_pool to python bindings

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9887 a83610d8-ad2a-0410-a6ab-fc0612d85776
support web seeds in magnet links

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9888 a83610d8-ad2a-0410-a6ab-fc0612d85776