Fix a build failure on AIX introduced after a change in the profile

    Fix a build failure on AIX introduced after a change in the profile
        of some of the "methods" in the target_ops structure.
        * aix-thread.c: Add missing target_ops parameter throughout.

        Implement Ada task switching on AIX.
        * aix-thread.c (aix_thread_get_ada_task_ptid): New function.
        (init_aix_thread_ops): Set aix_thread_ops.to_get_ada_task_ptid.