GET-BLOCK!, GET, and REDUCE

[hostilefork]

@hostilefork

This was the reason that GET-BLOCK! behavior was changed away from REDUCE.

It turns out it hadn't actually been changed yet, just written up that it should be changed to match GET of a BLOCK!.

But I'm questioning this assumption. Having :[x + 1 y * 2] act as reduce [x + 1 y * 2] seems much more useful.

I'm not sure how to reconcile this with not wanting GET of a BLOCK! to be a REDUCE. :-/ Rebol2, R3-Alpha, and Red all have no behavior for trying to get a block...it's an error. Maybe it's worth it to keep it that way so that there isn't a flagrant inconsistency?

I've also suggested higher purposes in the evaluator for SET-BLOCK!, for multiple return values. Hmm.