Issue 4884: Remove DECLARE_* translator callback macros

Issue 4884: Remove DECLARE_* translator callback macros

Recent changes have rendered them trivial.  This does not review their
accessibility status: in general, they should be protected since they
can be reused by derived classes but aren't needed externally.  However,
where they are indeed called from static member functions of derived
classes, the associated trampoline instantiation appears to require
public access.  This might warrant some more investigation.