Support longs in the register allocator for x86_64.

Change-Id: I7fb6dfb761bc5cf9e5705682032855a0a70ca867
diff --git a/compiler/optimizing/code_generator_x86.h b/compiler/optimizing/code_generator_x86.h
index acc670e..8a8216a 100644
--- a/compiler/optimizing/code_generator_x86.h
+++ b/compiler/optimizing/code_generator_x86.h
@@ -173,6 +173,10 @@
     return &move_resolver_;
   }
 
+  virtual InstructionSet GetInstructionSet() const OVERRIDE {
+    return InstructionSet::kX86;
+  }
+
  private:
   // Helper method to move a 32bits value between two locations.
   void Move32(Location destination, Location source);