Removal of VAX/VMS support

[DJ Delorie]

> If no one is maintaining a target it should go.

I agree, but how do you know nobody is maintaining it?  I say the
criteria is, if it breaks and nobody fixes it, then it's unmaintained.
Until then, we can't know that there isn't someone willing to fix it
who just happens to have nothing to do (for example, the djgpp target
hasn't been touched in ages, but works fine).

> If a platform is dead, it should go.

I disagree here.  We don't know it's dead until someone complains that
it doesn't work.

> The maintainers don't have the resources to spring clean all those
> obscure targets every time a core change is made.  Trying to this
> only results in much wasted effort and a bunch of buildable yet
> still broken targets.

I agree.  But that doesn't give us an excuse to dump a port that *is*
working.