usage.c: remove reference to busybox.h
*: s/include "busybox.h"/include "libbb.h"

diff --git a/networking/ping.c b/networking/ping.c
index e413bec..2f33191 100644
--- a/networking/ping.c
+++ b/networking/ping.c
@@ -27,7 +27,7 @@
 
 #include <net/if.h>
 #include <netinet/ip_icmp.h>
-#include "busybox.h"
+#include "libbb.h"
 
 #if ENABLE_PING6
 #include <netinet/icmp6.h>