xkcd-script: has fontlint

The fontforge "fontlint" suggests there are issues with the font:

```
Copyright (c) 2000-2014 by George Williams. See AUTHORS for Contributors.
License GPLv3+: GNU GPL version 3 or later
with many parts BSD . Please read LICENSE.
Based on sources from 22:38 UTC 29-Apr-2017-D.
Based on source from git with hash: b8e5ff8f24955f4d7d59ac73c903cc088b21bdb6
Internal Error: Attempt to unget two characters
CHECKING xkcd-script/font/xkcd-script.ttf
ERROR 5 Missing points at extrema
FAIL xkcd-script/font/xkcd-script.ttf
```

Looks like this will involve some post-processing of the contours, or a magic function buried within fontforge (probably already exists).