NetworkPkg: Source fixes and cleanup for ARMGCC compiles

- Fix EFI_IPv4_ADDRESS usages to use a macro to copy the structure
   instead of direct assignment, to avoid runtime alignment errors.
- Delete excess local variables that are initialized but otherwise unused.
- Add LibraryClasses.ARM & AARCH64 section in NetworkPkg.dsc file,
   containing a CompilerIntrinsicsLib null-library, required for successful
  standalone package builds (copied from MdeModulePkg.dsc).

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Randy Pawell <randy_pawell@hp.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>


git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16472 6f19259b-4bc3-4df7-8a09-765794883524

NetworkPkg/UefiPxeBcDxe/PxeBcDriver.c

@@ -1,6 +1,7 @@
 /** @file
   Driver Binding functions implementationfor for UefiPxeBc Driver.
 
+  (C) Copyright 2014 Hewlett-Packard Development Company, L.P.<BR>
   Copyright (c) 2007 - 2013, Intel Corporation. All rights reserved.<BR>
 
   This program and the accompanying materials
@@ -1400,7 +1401,6 @@ PxeBcStop (
   EFI_LOAD_FILE_PROTOCOL          *LoadFile;
   EFI_STATUS                      Status;
   EFI_HANDLE                      NicHandle;
-  BOOLEAN                         IsIpv6;
   PXEBC_PRIVATE_PROTOCOL          *Id;
 
   Private    = NULL;
@@ -1408,7 +1408,6 @@ PxeBcStop (
   VirtualNic = NULL;
   LoadFile   = NULL;
   Id         = NULL;
-  IsIpv6     = FALSE;
 
   Status = gBS->OpenProtocol (
                   ControllerHandle,