abstract generic_category() to build on boost-1.42 and older. fix some include issues in tests

test/dht_server.cpp

@@ -43,6 +43,10 @@ POSSIBILITY OF SUCH DAMAGE.
 #include <boost/shared_ptr.hpp>
 #include <boost/bind.hpp>
 
+#if defined TORRENT_DEBUG && TORRENT_USE_IOSTREAM
+#include <iostream>
+#endif
+
 using namespace libtorrent;
 
 struct dht_server