UefiCpuPkg: Add STM GUIDs, Protocols, and PCDs

* Add GUIDed HOB that described MSEG region in SMRAM
* Add SM Monitor Init Protocol
* Add PCD to configure size of SMM exception stack
* Add PCD to configure MSEG region size if it is not
  described by the gMsegSmramGuid GUIDed HOB.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>

UefiCpuPkg/Include/Guid/MsegSmram.h

@@ -0,0 +1,30 @@
+/** @file
+
+  Defines the HOB GUID used to describe the MSEG memory region allocated in PEI.
+
+  Copyright (c) 2015 - 2016, Intel Corporation. All rights reserved.<BR>
+  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.
+
+**/
+
+#ifndef _MSEG_SMRAM_H_
+#define _MSEG_SMRAM_H_
+
+#define MSEG_SMRAM_GUID \
+  { \
+    0x5802bce4, 0xeeee, 0x4e33, { 0xa1, 0x30, 0xeb, 0xad, 0x27, 0xf0, 0xe4, 0x39 } \
+  }
+
+extern EFI_GUID gMsegSmramGuid;
+
+//
+// The data portion of this HOB is type EFI_SMRAM_DESCRIPTOR
+//
+
+#endif