Subzero: Fix a build error. Also reformat.

src/IceMemory.cpp

 //===- subzero/src/IceMemory.cpp - Memory management definitions -*- C++ -*-==//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 20 matching lines @@
 void CfgAllocatorTraits::set_current(const manager_type *Manager) {
   ArenaAllocator *Allocator =
       Manager == nullptr ? nullptr : Manager->Allocator.get();
   set_current(Allocator);
 }
 
 void CfgAllocatorTraits::set_current(ArenaAllocator *Allocator) {
   ICE_TLS_SET_FIELD(CfgAllocator, Allocator);
 }
 
-void CfgAllocatorTraits::set_current(nullptr_t) {
+void CfgAllocatorTraits::set_current(std::nullptr_t) {
   ICE_TLS_SET_FIELD(CfgAllocator, nullptr);
 }
 
 ICE_TLS_DEFINE_FIELD(ArenaAllocator *, LivenessAllocatorTraits,
                      LivenessAllocator);
 
 LivenessAllocatorTraits::allocator_type LivenessAllocatorTraits::current() {
   return ICE_TLS_GET_FIELD(LivenessAllocator);
 }
 
 void LivenessAllocatorTraits::set_current(const manager_type *Manager) {
   ArenaAllocator *Allocator =
       Manager == nullptr ? nullptr : Manager->getAllocator();
   ICE_TLS_SET_FIELD(LivenessAllocator, Allocator);
 }
 } // end of namespace Ice