improve DHT logging a bit

git-svn-id: http://svn.code.sf.net/p/libtorrent/code/trunk@10346 a83610d8-ad2a-0410-a6ab-fc0612d85776
remove pointless DHT extension (for IPv6)

git-svn-id: http://svn.code.sf.net/p/libtorrent/code/trunk@10347 a83610d8-ad2a-0410-a6ab-fc0612d85776