gcc-13 rebind compile failure fix. Adding struct rebind for custom allocators as per this thread https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72792#c7

tests/src/unit-allocator.cpp

@@ -20,6 +20,11 @@ struct bad_allocator : std::allocator<T>
 {
     using std::allocator<T>::allocator;
 
+    template<typename U>
+    struct rebind {
+      using other = bad_allocator<U>;
+    };
+
     template<class... Args>
     void construct(T* /*unused*/, Args&& ... /*unused*/)
     {

tests/src/unit-regression2.cpp

@@ -187,6 +187,11 @@ std::string* sax_no_exception::error_string = nullptr;
 template<class T>
 class my_allocator : public std::allocator<T>
 {
+    template<typename U>
+    struct rebind {
+      using other = my_allocator<U>;
+    };
+
   public:
     using std::allocator<T>::allocator;
 };