Useless generated empty classes

[tritao]

In some cases we generate useless classes without any internals.

namespace BoostIPC
{
    public unsafe partial class win32_api
    {
        public partial struct Internal
        {
        }
    }

    namespace boost
    {
        public unsafe partial class win32_api
        {
            public partial struct Internal
            {
            }
        }

        namespace interprocess
        {
            public unsafe partial class win32_api
            {
                public partial struct Internal
                {
                }
            }