Fix build problems on Windows 64-bit by casting.

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 2781a8489885e43e72a572b29a4efda3a5c4272f..2c47cf84ce10fbac9b397605e394039783d47b37 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -46,17 +46,17 @@ MacroAssembler::MacroAssembler(void* buffer, int size)
 
 
 void MacroAssembler::LoadRoot(Register destination, Heap::RootListIndex index) {
-  movq(destination, Operand(r13, index << kPointerSizeLog2));
+  movq(destination, Operand(kRootRegister, index << kPointerSizeLog2));
 }
 
 
 void MacroAssembler::PushRoot(Heap::RootListIndex index) {
-  push(Operand(r13, index << kPointerSizeLog2));
+  push(Operand(kRootRegister, index << kPointerSizeLog2));
 }
 
 
 void MacroAssembler::CompareRoot(Register with, Heap::RootListIndex index) {
-  cmpq(with, Operand(r13, index << kPointerSizeLog2));
+  cmpq(with, Operand(kRootRegister, index << kPointerSizeLog2));
 }