support salt feature in DHT put

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9505 a83610d8-ad2a-0410-a6ab-fc0612d85776
fix client_test

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9506 a83610d8-ad2a-0410-a6ab-fc0612d85776
handle DHT error responses correctly

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9507 a83610d8-ad2a-0410-a6ab-fc0612d85776