[jnc_api] add utility: struct DualString (mainain both axl::sl::StringRef and cached jnc::DataPtr)
[jnc_api] add utility: struct DualString (mainain both axl::sl::StringRef and cached jnc::DataPtr)

vovkos/jancy,vovkos/jancy,vovkos/jancy,vovkos/jancy,vovkos/jancy