Feature request: ability to read heterogeneous types in FortranFile

At the moment, the three ``read_*`` methods of ``scipy.io.FortranFile`` can only read records with homogeneous data types, but it would be nice to allow some more flexibiity, for cases where the data is written e.g. as:

```
write(10) some_int, some_float
```

I was thinking that we could add a new method ``read_mixed`` that could take a list of dtypes, and returns a Python list with scalars inside.

I could look into it if there was interest in having such a feature in scipy.