Fix the GC branch so it compiles and runs on 64 bit.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
===================================================================
--- src/x64/macro-assembler-x64.h	(revision 7889)
+++ src/x64/macro-assembler-x64.h	(working copy)
@@ -59,6 +59,11 @@
 // Convenience for platform-independent signatures.
 typedef Operand MemOperand;
 
+enum EmitRememberedSet { EMIT_REMEMBERED_SET, OMIT_REMEMBERED_SET };
+enum SmiCheck { INLINE_SMI_CHECK, OMIT_SMI_CHECK };
+
+bool Aliasing(Register r1, Register r2, Register r3, Register r4);
+
 // Forward declaration.
 class JumpTarget;