Enable Tie Option

Espeak has an additional parameter --tie to enable the tie character 

```
espeak-ng 'Hello' -v en-us --ipa -q
həlˈoʊ
```

as opposed to:

```
espeak-ng 'Hello' -v en-us --ipa -q --tie
həlˈo͡ʊ
```

Would it be possible to add an option to enable this?

