[tree-ssa] garbage collectable CFG

[S. Bosscher]

> > Not quite true.  There are two sets of rtl hooks.  Just make
> > it tree or rtl.
> 
> Well, in fact there are three, the third set is
> cfg_layout_rtl_cfg_hooks.

Ehm, which is exactly what you said of course :-/

(slams head into wall screaming "read man, read!")

So "GTY ((desc ("cfg_hooks == &tree_cfg_hooks ? 2 : 1")" is TRT here.
I'll commit it with that change.

Gr.
Steven