Rename A64 port to ARM64 port

src/arm64/lithium-arm64.cc

Index: src/arm64/lithium-arm64.cc
diff --git a/src/a64/lithium-a64.cc b/src/arm64/lithium-arm64.cc
similarity index 99%
rename from src/a64/lithium-a64.cc
rename to src/arm64/lithium-arm64.cc
index c5501010a5c57fb91a0712e00bdaf02e19a482cf..c6f547f6284db0dcccc091f52f21b02f3f9c8688 100644
--- a/src/a64/lithium-a64.cc
+++ b/src/arm64/lithium-arm64.cc
@@ -28,8 +28,8 @@
 #include "v8.h"
 
 #include "lithium-allocator-inl.h"
-#include "a64/lithium-a64.h"
-#include "a64/lithium-codegen-a64.h"
+#include "arm64/lithium-arm64.h"
+#include "arm64/lithium-codegen-arm64.h"
 #include "hydrogen-osr.h"
 
 namespace v8 {
@@ -2456,7 +2456,7 @@ LInstruction* LChunkBuilder::DoUnaryMathOperation(HUnaryMathOperation* instr) {
     case kMathFloor: {
       ASSERT(instr->representation().IsInteger32());
       ASSERT(instr->value()->representation().IsDouble());
-      // TODO(jbramley): A64 can easily handle a double argument with frintm,
+      // TODO(jbramley): ARM64 can easily handle a double argument with frintm,
       // but we're never asked for it here. At the moment, we fall back to the
       // runtime if the result doesn't fit, like the other architectures.
       LOperand* input = UseRegisterAtStart(instr->value());