Fix processor to build with clang

src/processor/linked_ptr.h

Index: src/processor/linked_ptr.h
===================================================================
--- a/src/processor/linked_ptr.h
+++ b/src/processor/linked_ptr.h
@@ -123,17 +123,17 @@ class linked_ptr {
   // Smart pointer members.
   void reset(T* ptr = NULL) { depart(); capture(ptr); }
   T* get() const { return value_; }
   T* operator->() const { return value_; }
   T& operator*() const { return *value_; }
   // Release ownership of the pointed object and returns it.
   // Sole ownership by this linked_ptr object is required.
   T* release() {
-    bool last = link_.depart();
+    link_.depart();
     T* v = value_;
     value_ = NULL;
     return v;
   }
 
   bool operator==(T* p) const { return value_ == p; }
   bool operator!=(T* p) const { return value_ != p; }
   template <typename U>