Another way to get unique wave ids

[Garados007]

In case our current hacky approach does no longer work, we can use this one:

1. Make the wave global
2. Display it (e.g. Display wv)
3. Call GetWindow on it to retrieve the wave list (e.g. GetWindow Graph0, wavelist)
4. Look into the third column of W_WaveList to get a wave id

This approach has many downsides, including making the wave global and displaying it.