refactor: remove references to deprecated values under std::allocator

Includes allocator::pointer, allocator::const_pointer, allocator::reference and allocator::const_reference which are deprecated in c++17 and removed in c++20. See https://en.cppreference.com/w/cpp/memory/allocator

Also prefer `using` over `typedef` see: https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rt-using

src/support/allocators/secure.h

@@ -9,6 +9,7 @@
 #include <support/lockedpool.h>
 #include <support/cleanse.h>
 
+#include <memory>
 #include <string>
 
 //
@@ -17,15 +18,13 @@
 //
 template <typename T>
 struct secure_allocator : public std::allocator<T> {
-    // MSVC8 default copy constructor is broken
-    typedef std::allocator<T> base;
-    typedef typename base::size_type size_type;
-    typedef typename base::difference_type difference_type;
-    typedef typename base::pointer pointer;
-    typedef typename base::const_pointer const_pointer;
-    typedef typename base::reference reference;
-    typedef typename base::const_reference const_reference;
-    typedef typename base::value_type value_type;
+    using base = std::allocator<T>;
+    using traits = std::allocator_traits<base>;
+    using size_type = typename traits::size_type;
+    using difference_type = typename traits::difference_type;
+    using pointer = typename traits::pointer;
+    using const_pointer = typename traits::const_pointer;
+    using value_type = typename traits::value_type;
     secure_allocator() noexcept {}
     secure_allocator(const secure_allocator& a) noexcept : base(a) {}
     template <typename U>

src/support/allocators/zeroafterfree.h

@@ -13,15 +13,13 @@
 
 template <typename T>
 struct zero_after_free_allocator : public std::allocator<T> {
-    // MSVC8 default copy constructor is broken
-    typedef std::allocator<T> base;
-    typedef typename base::size_type size_type;
-    typedef typename base::difference_type difference_type;
-    typedef typename base::pointer pointer;
-    typedef typename base::const_pointer const_pointer;
-    typedef typename base::reference reference;
-    typedef typename base::const_reference const_reference;
-    typedef typename base::value_type value_type;
+    using base = std::allocator<T>;
+    using traits = std::allocator_traits<base>;
+    using size_type = typename traits::size_type;
+    using difference_type = typename traits::difference_type;
+    using pointer = typename traits::pointer;
+    using const_pointer = typename traits::const_pointer;
+    using value_type = typename traits::value_type;
     zero_after_free_allocator() noexcept {}
     zero_after_free_allocator(const zero_after_free_allocator& a) noexcept : base(a) {}
     template <typename U>