Improper output when importing core.stdc.limits

When I attempt to convert [this header](https://github.com/wch/r-source/blob/trunk/src/include/R.h), the top looks like this:

```
eximport core.stdc.limits;

tern (C):
```

This is not the first time I've encountered this, but it's the first time I thought to report it when it happened.