make a64 compile on mavericks

src/a64/assembler-a64.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 38 matching lines @@
 R(8)  R(9)  R(10) R(11) R(12) R(13) R(14) R(15)                                \
 R(16) R(17) R(18) R(19) R(20) R(21) R(22) R(23)                                \
 R(24) R(25) R(26) R(27) R(28) R(29) R(30) R(31)
 
 
 static const int kRegListSizeInBits = sizeof(RegList) * kBitsPerByte;
 
 
 // Some CPURegister methods can return Register and FPRegister types, so we
 // need to declare them in advance.
-class Register;
-class FPRegister;
+struct Register;
+struct FPRegister;
 
 
 struct CPURegister {
   enum RegisterType {
     // The kInvalid value is used to detect uninitialized static instances,
     // which are always zero-initialized before any constructors are called.
     kInvalid = 0,
     kRegister,
     kFPRegister,
     kNoRegister
@@ skipping 1965 matching lines @@
 class EnsureSpace BASE_EMBEDDED {
  public:
   explicit EnsureSpace(Assembler* assembler) {
     assembler->CheckBuffer();
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_A64_ASSEMBLER_A64_H_