add_role and remove_role on a Class PMC

[Stephen Weeks]

Not long ago, Jonathan Duke Leto proclaimed...
> Rakudo Perl 6 got along quite well with Parrot's paper-clips-and-glue object
> system. I think a short term goal should be to improve it enough to try and
> unblock Cardinal.
FWIW, my plans for Cardinal are to build off of 6model, like Rakudo is
doing in its nom branch.  If/when Parrot backports functionality from
6model, we'll want to migrate to using that, certainly, but I'm
certainly content with using 6model for now.