program_options.hpp fails when imported as a header unit (MSVC 2022).

The program fails to compile when trying to import `program_options.hpp` as a header unit in Visual Studio 2022 (C++20).

main.cpp
```
import ;

int main(int argc, char** argv)
{
namespace po = boost::program_options;
po::options_description desc;
desc.add_options()
("stringtest", po::value()->implicit_value("test"), "string test")
;

return 0;
}
```

You'll get the following error:
`Error - C3084 - 'boost::exception::~exception': a destructor cannot be 'abstract' - solution - E:\Projects\CPP\boost\boost\exception\exception.hpp - 297`

I haven't had any troubles with any other boost headers. This is the only one I've run into with this issue. This was tested with the latest master branch.

Comienza compilando el main.cpp proporcionado con MSVC 2022 en modo C++20 e importando boost/program_options.hpp como header unit. Inspecciona boost/exception/exception.hpp alrededor de la línea 297 mientras comparas el fallo de la header unit con un include normal. Se considera terminado cuando el ejemplo compila correctamente con la importación como header unit.

Escrito por el modelo de indexación a partir del texto del issue.