Primitive Array/Hash PMCs

Since not all languages targetting Parrot need or want neato things
like aggregate keys, I propose that they be left to the Perl* stuff and we
make the default Array/Hash very simple, but fast primitive versions.

That means a plain Array will be able to use Ix registers directly
as subscripts without creating a KEY struct.

-Melvin

• Primitive Array/Hash PMCs by Melvin Smith