1.0.9.57: allow pv-optimizations for typechecking (SETF SLOT-VALUE)

1.0.9.57: allow pv-optimizations for typechecking (SETF SLOT-VALUE)

* For each optimized access, store both the slot location and the
  typecheck function in the permutation vector. If the write is in
  safe code, use the typecheck function to validate the new value
  before using it.

* Approximately ~5x as fast as SAFE-SET-SLOT-VALUE -- which is still
  needed in a few places as ACCESSOR-SET-SLOT-VALUE doesn't do type
  checking.