ART: Add -Wunused

Until the global CFLAGS are fixed, add Wunused. Fix declarations
in the optimizing compiler.

Change-Id: Ic4553f08e809dc54f3d82af57ac592622c98e000
diff --git a/compiler/optimizing/inliner.h b/compiler/optimizing/inliner.h
index 8e9cf83..2b08d3d 100644
--- a/compiler/optimizing/inliner.h
+++ b/compiler/optimizing/inliner.h
@@ -35,13 +35,15 @@
            CompilerDriver* compiler_driver,
            OptimizingCompilerStats* stats,
            size_t depth = 0)
-      : HOptimization(outer_graph, true, "inliner", stats),
+      : HOptimization(outer_graph, true, kInlinerPassName, stats),
         outer_compilation_unit_(outer_compilation_unit),
         compiler_driver_(compiler_driver),
         depth_(depth) {}
 
   void Run() OVERRIDE;
 
+  static constexpr const char* kInlinerPassName = "inliner";
+
  private:
   bool TryInline(HInvoke* invoke_instruction, uint32_t method_index, InvokeType invoke_type) const;