MdePkg BaseLib: Add the missing nasm source file InternalSwitchStack.nasm

BaseLib Ia32 InternalSwitchStack.S has no matched InternalSwitchStack.nasm.
Use ObjDump to verify the output object files be same.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>

MdePkg/Library/BaseLib/Ia32/InternalSwitchStack.nasm

@@ -0,0 +1,47 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2016, Intel Corporation. All rights reserved.<BR>
+; Portions copyright (c) 2011, 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
+; 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:
+;
+;   InternalSwitchStack.nasm
+;
+; Abstract:
+;
+;   Implementation of a stack switch on IA-32.
+;
+;------------------------------------------------------------------------------
+
+    SECTION .text
+
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; InternalSwitchStack (
+;   IN      SWITCH_STACK_ENTRY_POINT  EntryPoint,
+;   IN      VOID                      *Context1,   OPTIONAL
+;   IN      VOID                      *Context2,   OPTIONAL
+;   IN      VOID                      *NewStack
+;   );
+;------------------------------------------------------------------------------
+global ASM_PFX(InternalSwitchStack)
+ASM_PFX(InternalSwitchStack):
+  push  ebp
+  mov   ebp, esp
+
+  mov   esp, [ebp + 20]    ; switch stack
+  sub   esp, 8
+  mov   eax, [ebp + 16]
+  mov   [esp + 4], eax
+  mov   eax, [ebp + 12]
+  mov   [esp], eax
+  push  0                  ; keeps gdb from unwinding stack
+  jmp   dword [ebp + 8]    ; call and never return