iputils: Move the iputils tools to packages

Per discussion in https://github.com/openwrt/openwrt/pull/1804, iputils is
moving from the main openwrt repository to the packages feed, and is switching
from the abandoned skbuff.net upstream to github.com/iputils/iputils

Signed-off-by: Noah Meyerhans <frodo@morgul.net>

net/iputils/Config_ping.in

@@ -0,0 +1,17 @@
+if PACKAGE_iputils-ping
+
+config PING_LEGACY_SYMLINKS
+	bool
+	default n
+	prompt "Install legacy ping4 and ping6 symlinks"
+	help
+		Iputils previously generated separate "ping" and "ping6"
+		binaries for supporting IPv4 and IPv6 communication,
+		respectively.  Recent versions of iputils have merged
+		support for both address families into a single program.
+		Select this option to install "ping6" and "ping4" symlinks
+		to the unified binary to support compatibility with
+		existing tools that may still expect to find the old
+		names.
+
+endif