Use unsigned int instead of int for refcount for libxml objects (#15247)

Author: nielsdos

UPGRADING.INTERNALS

@@ -301,6 +301,7 @@ PHP 8.4 INTERNALS UPGRADE NOTES
    - Added php_libxml_uses_internal_errors().
    - Added a way to override document handlers (e.g. serialization) with
      php_libxml_document_handlers.
+   - Changed the refcount fields from int to unsigned int.
 
  e. ext/date
    - Added the php_format_date_ex() API to format instances of php_date_obj.

ext/dom/document.c

@@ -1243,7 +1243,7 @@ PHP_METHOD(DOMDocument, __construct)
 	dom_object *intern;
 	char *encoding, *version = NULL;
 	size_t encoding_len = 0, version_len = 0;
-	int refcount;
+	unsigned int refcount;
 
 	if (zend_parse_parameters(ZEND_NUM_ARGS(), "|ss", &version, &version_len, &encoding, &encoding_len) == FAILURE) {
 		RETURN_THROWS();
@@ -1476,7 +1476,7 @@ static void php_dom_finish_loading_document(zval *this, zval *return_value, xmlD
 			php_libxml_decrement_node_ptr((php_libxml_node_object *) intern);
 			doc_prop = intern->document->doc_props;
 			intern->document->doc_props = NULL;
-			int refcount = php_libxml_decrement_doc_ref((php_libxml_node_object *)intern);
+			unsigned int refcount = php_libxml_decrement_doc_ref((php_libxml_node_object *)intern);
 			if (refcount != 0) {
 				docp->_private = NULL;
 			}

ext/libxml/php_libxml.h

@@ -113,14 +113,14 @@ typedef struct _php_libxml_ref_obj {
 	php_libxml_cache_tag cache_tag;
 	php_libxml_private_data_header *private_data;
 	const php_libxml_document_handlers *handlers;
-	int refcount;
+	unsigned int refcount;
 	php_libxml_class_type class_type : 8;
 	php_libxml_quirks_mode quirks_mode : 8;
 } php_libxml_ref_obj;
 
 typedef struct _php_libxml_node_ptr {
 	xmlNodePtr node;
-	int	refcount;
+	unsigned int refcount;
 	void *_private;
 } php_libxml_node_ptr;