Added peek() to ptr_vec.

src/rt/rust_internal.h

@@ -151,6 +151,7 @@ public:
     T *& operator[](size_t offset);
     void push(T *p);
     T *pop();
+    T *peek();
     void trim(size_t fill);
     void swap_delete(T* p);
 };

src/rt/rust_util.h

@@ -69,6 +69,13 @@ ptr_vec<T>::pop()
     return data[--fill];
 }
 
+template <typename T>
+T *
+ptr_vec<T>::peek()
+{
+    return data[fill - 1];
+}
+
 template <typename T>
 void
 ptr_vec<T>::trim(size_t sz)