Fix ia64 breakpoints in the L-X slot.

    Fix ia64 breakpoints in the L-X slot.
        * ia64-tdep.c (ia64_memory_insert_breakpoint): Extend the comment.
        New variable shadow_slotnum, use it appropriately instead of slotnum.
        Move shadow_len initialization before SLOTNUM adjustment, cover now the
        whole remaining bundle.  Error now on breakpoints requested for the
        slot 2 of L-X bundles.  Better sanity check the requested slot 1 of L-X
        bundles.
        (ia64_memory_remove_breakpoint): New variable shadow_slotnum, use it
        appropriately instead of slotnum.  Warn now on breakpoints requested
        for the slot 2 of L-X bundles.  Better sanity check the requested slot
        1 of L-X bundles.  Update the assertio check of PLACED_SIZE.
        (ia64_breakpoint_from_pc): New variable shadow_slotnum, use it
        appropriately instead of slotnum.  Move *lenptr initialization before
        SLOTNUM adjustment, cover now the whole remaining bundle.  Error now
        on breakpoints requested for the slot 2 of L-X bundles.  Better sanity
        check the requested slot 1 of L-X bundles.  Simplify the returned
        expression.