hoa.gain~ with max-api

need to fix several issues with hoa.gain~ object when compiled against the new max-api:
- preset disabled (the method binbuf_vinsert does not exists anymore)
- error message when instantiated : 

```
zgetfn (bfixwidth): corrupt object
method bfixwidth called on invalid object
```

=> see: beafec52f3fd03d19dd3d4f811192c47e562404d
