1.0.17.9: grab-bag of PCL hackery

1.0.17.9: grab-bag of PCL hackery

 * Make REAL-ADD-METHOD suck slightly less: instead of paying for
   generic dispatch for all METHOD-FOO accessors, use a single call
   to a method that gets the benefit of permutation vectors and
   returns all we want as multiple values.

   ...this assumes that users are not allowed to override METHOD-FOO
   accessors. My current reading of AMOP is that overriding them is
   not specified at all -- but if someone needs it, we can use
   CLASS-EQ specializer magic to make that work.

 * A smattering of :TEST #'EQs for PUSHNEW, MEMBER, and ADJOIN.

 * Global specializer tables need to be synchronized now that our
   hash-tables aren't thread safe by default anymore.