Buffer prof_log_stop

Make use of the new buffered writer for the output of `prof_log_stop`.

test/unit/prof_log.c

@@ -61,7 +61,7 @@ static void *f_thread(void *unused) {
 	int i;
 	for (i = 0; i < N_PARAM; i++) {
 		void *p = malloc(100);
-		memset(p, 100, sizeof(char));
+		memset(p, 100, 1);
 		free(p);
 	}