logging extend level set api to allow setting emission function

Signed-off-by: Andy Green <andy.green@linaro.org>
diff --git a/test-server/test-ping.c b/test-server/test-ping.c
index 93df59e..bc03100 100644
--- a/test-server/test-ping.c
+++ b/test-server/test-ping.c
@@ -339,7 +339,7 @@
 			continue;
 		switch (n) {
 		case 'd':
-			lws_set_log_level(atoi(optarg));
+			lws_set_log_level(atoi(optarg), NULL);
 			break;
 		case 'm':
 			use_mirror = 1;