C++11: Use template aliases instead of inheritance

util/stdlib/pointer_container.h

Index: util/stdlib/pointer_container.h
diff --git a/util/stdlib/pointer_container.h b/util/stdlib/pointer_container.h
index 23c35d7c2630833dfbcb20fc060e0cc31a26738c..cb3e83643fded849897f46e486643d91526b221e 100644
--- a/util/stdlib/pointer_container.h
+++ b/util/stdlib/pointer_container.h
@@ -50,7 +50,7 @@ class PointerContainer : public ContainerType {
 //! \note No attempt is made to `delete` elements that are removed from the
 //!     vector by other means, such as replacement or `clear()`.
 template <typename T>
-class PointerVector : public PointerContainer<std::vector<T*>> {};
+using PointerVector = PointerContainer<std::vector<T*>>;
 
 }  // namespace crashpad