Import Library Class from original MDE package. Also I added the EFI_PEI_CORE_ENTRY_POINT definition in PiPeiCis.h.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@2677 6f19259b-4bc3-4df7-8a09-765794883524

MdePkg/Include/Library/UefiRuntimeServicesTableLib.h

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+/** @file
+  Library that provides a global pointer to the UEFI Runtime Services Tables
+
+  Copyright (c) 2006, Intel Corporation
+  All rights reserved. This program and the accompanying materials
+  are licensed and made available under the terms and conditions of the BSD License
+  which accompanies this distribution.  The full text of the license may be found at
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+  Module Name:  UefiRuntimeServicesTableLib.h
+
+**/
+
+#ifndef __UEFI_RUNTIME_SERVICES_TABLE_LIB_H__
+#define __UEFI_RUNTIME_SERVICES_TABLE_LIB_H__
+
+//
+// Cached copy of the EFI Runtime Services Table
+//
+extern EFI_RUNTIME_SERVICES  *gRT;
+
+#endif