Root-relative namespace keys

[Allison Randal]

Patrick R. Michaud wrote:
> 
> When I try this in current trunk (r35084), I get:
> 
>   $ cat x.pir
>   .sub 'main'
>       $P0 = box 3
>       $P99 = get_root_namespace ['parrot';'Foo';'Bar']
>       $I0 = isa $P0, $P99
>       say $I0
>   .end
> 
>   $ ./parrot x.pir
>   Null PMC access in isa_pmc()
>   current instr.: 'main' pc 6 (x.pir:4)
>   $


But, the first line of the 'isa_pmc' vtable function is:

         if (PMC_IS_NULL(lookup))
             return 0;

If it's throwing a null PMC access exception, that's a bug.

Allison