Change the register allocator so that it no longer tracks references...

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
===================================================================
--- src/x64/assembler-x64.cc	(revision 2055)
+++ src/x64/assembler-x64.cc	(working copy)
@@ -568,16 +568,6 @@
   return NULL;
 }
 
-bool RegisterAllocator::IsReserved(int a) {
-  UNIMPLEMENTED();
-  return false;
-}
-
-RegisterFile RegisterAllocator::Reserved() {
-  UNIMPLEMENTED();
-  return RegisterFile();
-}
-
 const int RelocInfo::kApplyMask = -1;
 
 StackFrame::Type StackFrame::ComputeType(StackFrame::State* a) {