null termination where the null terminator is a int32
when I use `terminator=0` It stops on the first byte that is 0 but I don't want it to stop until it gets to an int32 (`s4`)  that is zero.
 I am having a hard time figuring out how to do that.

The following seems to work, but then this needs to get converted to a string?
```yaml
      - id: str_things
        type: s4
        # encoding: UTF-8
        # terminator: 0
        repeat: until
        repeat-until: _ == 0
```

additionally  I want to read in a list of variable names.

given by
```yaml
      - id: number_vars
        type: s4
```
where `number_vars` is the number of variable names I want to parse where each variable name has length n_chars+1, as each variable names is terminated with a 0 int32 value.
 