Implement IPv6/IPv4 ping.

Change-Id: Id53797c795c17fbacce3659c945f5126dc9dee86
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>
diff --git a/vnet/Makefile.am b/vnet/Makefile.am
index 71680b9..1c28ebc 100644
--- a/vnet/Makefile.am
+++ b/vnet/Makefile.am
@@ -258,6 +258,7 @@
  vnet/ip/icmp6.c				\
  vnet/ip/ip_feature_registration.c		\
  vnet/ip/ip46_cli.c				\
+ vnet/ip/ping.c					\
  vnet/ip/ip4_format.c				\
  vnet/ip/ip4_forward.c				\
  vnet/ip/ip4_input.c				\