Syntax clean up to make clang happy.

Change-Id: I0984c395bbd1ee4b206eafd19915b6f68781dd16
diff --git a/src/dex_instruction_visitor.h b/src/dex_instruction_visitor.h
index 2808c97..d625b64 100644
--- a/src/dex_instruction_visitor.h
+++ b/src/dex_instruction_visitor.h
@@ -61,7 +61,7 @@
 #undef INSTRUCTION_VISITOR
 
   // The default instruction handler.
-  void Do_Default(const Instruction* inst) {
+  void Do_Default(const Instruction*) {
     return;
   }
 };