avoid definition collision with gcc 11 (see @bartoszek description of the issue (#491) for more detail

src/pdf-merger/Object.cpp

@@ -278,7 +278,7 @@ void Object::serialize(std::ofstream & out, std::map< unsigned int, std::pair<un
 
    sizesAndGenerationNumbers.insert(std::pair<unsigned int, std::pair<unsigned long long, unsigned int > >(_number, std::make_pair(objectSizeForXref, _generationNumber)));
 
-   _serialize(out, stream);
+   serialize(out, stream);
    stream.clear();
    stream.reserve();
 
@@ -429,7 +429,7 @@ void Object::_addParent(Object * child)
 {
    _parents.insert(child);
 }
-void Object::_serialize(std::ofstream  & out, const std::string & stream)
+void Object::serialize(std::ofstream  & out, const std::string & stream)
 {
     out << _number << " " << _generationNumber << " obj\n" << _content << stream << "endobj\n";
    out.flush();

src/pdf-merger/Object.h

@@ -152,11 +152,11 @@ namespace merge_lib
        void _setObjectNumber(unsigned int objectNumber);       
        void _addParent(Object * child);
        bool _findObject(const std::string & token, Object* & foundObject, unsigned int & tokenPositionInContent);
-       void _serialize(std::ofstream  & out, const std::string & stream);
+       void serialize(std::ofstream  & out, const std::string & stream);
        void _recalculateObjectNumbers(unsigned int & maxNumber);
        void _recalculateReferencePositions(unsigned int changedReference, int displacement);
        void _retrieveMaxObjectNumber(unsigned int & maxNumber);
-       void _serialize(std::ofstream & out, std::map<unsigned int, unsigned long long> & sizes);       
+       void serialize(std::ofstream & out, std::map<unsigned int, unsigned long long> & sizes);
        bool _getStreamFromContent(std::string & stream);
 
        //members