Release RTL bodies after compilation (sometimes)

[Daniel Berlin]

> Actually, it's not an effect at all.  You can only safely use ggc_free
> on an object which is not referenced.  Objects which are not
> referenced are not marked.

This isn't necessarily true.

You may forget to null out the pointer, accidently keeping it, and what 
it points to, live (since unless it's marked deletable, the gc doesn't 
know it can null it for you).

>Therefore, ggc_free does not change the
> number of objects marked.

Therefore, this isn't true either.
It would be true if the pointer was reset to null before collection, but 
if not, then ggc_free can change the number of objects marked.

>