Task description: Add an opcode 'copy' to src/ops/set.ops. Similar to 'clone'.
- It takes two PMC arguments - It calls VTABLE_morph on $1, and then VTABLE_assign on the two. - It needs to call VTABLE_type to get the type of the source PMC to pass to 'morph' instead of calling $1->vtable->base_type, because the base_type won't be right for Object PMCs.
