AK: Add OwnPtrWithCustomDeleter

This class is a smart pointer that let you provide a custom deleter to
free the pointer.

It is quite primitive compared to other smart pointers but can still be
useful when interacting with C types that provides a custom `free()`
function.

AK/OwnPtrWithCustomDeleter.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2022, Lucas Chollet <lucas.chollet@free.fr>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/Noncopyable.h>
+#include <AK/StdLibExtras.h>
+
+template<typename T>
+struct OwnPtrWithCustomDeleter {
+    AK_MAKE_NONCOPYABLE(OwnPtrWithCustomDeleter);
+
+public:
+    OwnPtrWithCustomDeleter(T* ptr, Function<void(T*)> deleter)
+        : m_ptr(ptr)
+        , m_deleter(move(deleter))
+    {
+    }
+
+    OwnPtrWithCustomDeleter(OwnPtrWithCustomDeleter&& other)
+    {
+        swap(m_ptr, other.m_ptr);
+        swap(m_deleter, other.m_deleter);
+    };
+
+    ~OwnPtrWithCustomDeleter()
+    {
+        if (m_ptr) {
+            VERIFY(m_deleter);
+            m_deleter(m_ptr);
+        }
+    }
+
+private:
+    T* m_ptr { nullptr };
+    Function<void(T*)> m_deleter {};
+};