export ed25519 functions from libtorrent. fix tools/dht_put build when dht is disabled. fix shared linking in tools Jamfile

tools/dht_put.cpp

@@ -43,6 +43,16 @@ POSSIBILITY OF SUCH DAMAGE.
 
 using namespace libtorrent;
 
+#ifdef TORRENT_DISABLE_DHT
+
+int main(int argc, char* argv[])
+{
+	fprintf(stderr, "not built with DHT support\n");
+	return 1;
+}
+
+#else
+
 void usage()
 {
 	fprintf(stderr,
@@ -313,3 +323,5 @@ int main(int argc, char* argv[])
 	fclose(f);
 }
 
+#endif
+