[RFC] Amiga/VMS cleanup

The removal of most items was pretty straightforward, but I have one question. I noticed that `runtime/doc/develop.txt` states this:
```
Function names can not be more than 31 characters long (because of VMS).
```
Does anyone know if this is still true? If it's not, I'd like to remove it.
Can just remove the entire sentence. 

Any case platform support is listed for all platforms we support, we can (and should) just remove the statement entirely.