rp-pppoe: Add back from oldpackages with build fixes and enhanced packaging

Add back from oldpackages with fixes for build errors and UCIfication
(for LuCI app submitted in a related PR (against LuCI repo)).

NOTE: Untested packages have been marked with @BROKEN.  This can
be undone of others report success with the sniffer

Signed-off-by: Daniel Dickinson <lede@daniel.thecshore.com>

net/rp-pppoe/files/pppoe-server.default

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+if [ -e /etc/default/pppoe-server ]; then
+	if [ -z "$(uci get pppoe.@pppoe_server[-1] 2>/dev/null)" ]; then
+		uci add pppoe pppoe_server_
+	fi
+	uci set pppoe.@pppoe-server[-1].use_non_uci_config=1
+	uci commit pppoe
+fi
+