[dvipdfmx] pdf:mapline not properly released warning

[Hironobu Yamashita]

Hi,

The following code using pdf:mapline special throws
strange warnings

dvipdfmx:warning: font "HaranoAjiMincho-Heavy.otf" not properly released?
dvipdfmx:warning: font "uprml-hq" not properly released?

Is this behavior expected?

```
\documentclass{ujarticle}
\AtBeginDvi{\special{pdf:mapline uprml-h UniJIS-UTF16-H
HaranoAjiMincho-Bold.otf}}
\AtBeginDvi{\special{pdf:mapline uprml-hq UniJIS-UCS2-H
HaranoAjiMincho-Heavy.otf}}
\begin{document}
テスト
\end{document}
```

Best regards,
Hironobu Yamashita