Rename `_AUD3WAVERAM` to `AUD3WAVERAM`

[Rangi42]

We already renamed _SCRN0/_SCRN1 to TILEMAP0/TILEMAP1. In general we shouldn't be starting library constants with an underscore; it looks like the sort of _NARG constant that RGBASM defines as a built-in.

Non-underscore AUD3WAVERAM would be fine.