MdePkg: Define IPv4_ADDRESS and IPv6_ADDRESS in Base.h

Since the following patch needs to add API converting string
to IP address in BaseLib, define the IP address as base types
in Base.h.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

MdePkg/Include/Base.h

@@ -6,7 +6,7 @@
   environment. There are a set of base libraries in the Mde Package that can
   be used to implement base modules.
 
-Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.<BR>
 Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
@@ -265,6 +265,20 @@ typedef struct {
   UINT8   Data4[8];
 } GUID;
 
+///
+/// 4-byte buffer. An IPv4 internet protocol address.
+///
+typedef struct {
+  UINT8 Addr[4];
+} IPv4_ADDRESS;
+
+///
+/// 16-byte buffer. An IPv6 internet protocol address.
+///
+typedef struct {
+  UINT8 Addr[16];
+} IPv6_ADDRESS;
+
 //
 // 8-bytes unsigned value that represents a physical system address.
 //