[tree-ssa] Garbage collector x bb annotations

[Daniel Berlin]

>
> Plus, right now the compiler crashes, which is much faster than all
> that tedious code generation...
>
> The right thing to do is to allow GC to improve data locality.  I
> believe Dan Berlin had some patches for this, although I don't know
> their state.

Uh, well, the zone collector was updated per your comments, and is 
awaiting review again.

--Dan