add ':' (colon) as valid char for an XML tag

[TobiasLange75443]

According to the description https://www.boost.org/doc/libs/1_81_0/libs/serialization/doc/exceptions.html#xml_archive_tag_name_error -> xml_archive_tag_name_error ':' (colon) is a valid character for XML tag names. But if a colon is used in a tag name, an xml_archive_tag_name_error - exception is thrown. The code change defines ':' colon as valid character.

Examplecode:

#include <iostream>
#include <sstream>
#include <string>
#include <boost/archive/xml_oarchive.hpp>
#include <boost/archive/xml_iarchive.hpp>
#include <boost/archive/xml_archive_exception.hpp>
#include <boost/archive/impl/basic_xml_oarchive.ipp>

int main()
{
  try
  {
    boost::archive::detail::XML_name<const char>{}(':');
  }
  catch (boost::archive::xml_archive_exception& e)
  {
    std::cout << e.what();
  }

  const auto tag{ "A:B" };
  std::ostringstream oss;
  {
    try
    {
      boost::archive::xml_oarchive oa{ oss };
      int value{ 25 };
      oa << boost::serialization::make_nvp(tag, value);
    }
    catch (boost::archive::xml_archive_exception& e)
    {
      std::cout << e.what();
    }
  }
  std::cout << oss.str();
  {
    std::istringstream iss{ oss.str() };
    boost::archive::xml_iarchive ia{ iss };
    int value{ 0 };
    ia >> boost::serialization::make_nvp(tag, value);
  }

  return 0;
}