[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.
I'll do that for this line, but one question.

> "Unix" applies to OS X here

Can the same be said for the majority of other `Macintosh` mentions?