nhrpd: implement next hop resolution protocol

This provides DMVPN support and integrates to strongSwan. Please read
README.nhrpd and README.kernel for more details.
diff --git a/nhrpd/vici.h b/nhrpd/vici.h
new file mode 100644
index 0000000..24b900b
--- /dev/null
+++ b/nhrpd/vici.h
@@ -0,0 +1,24 @@
+
+enum vici_type_t {
+	VICI_START =         0,
+	VICI_SECTION_START = 1,
+	VICI_SECTION_END =   2,
+	VICI_KEY_VALUE =     3,
+	VICI_LIST_START =    4,
+	VICI_LIST_ITEM =     5,
+	VICI_LIST_END =      6,
+	VICI_END =           7
+};
+
+enum vici_operation_t {
+	VICI_CMD_REQUEST = 0,
+	VICI_CMD_RESPONSE,
+	VICI_CMD_UNKNOWN,
+	VICI_EVENT_REGISTER,
+	VICI_EVENT_UNREGISTER,
+	VICI_EVENT_CONFIRM,
+	VICI_EVENT_UNKNOWN,
+	VICI_EVENT,
+};
+
+#define VICI_MAX_MSGLEN		(512*1024)