Ensure ptrace() calls cast arguments 3 and 4 appropriately.

        * linux-low.c (handle_extended_wait, linux_create_inferior)
        (linux_attach_lwp_1, linux_kill_one_lwp, linux_attach_one_lwp)
        (dequeue_one_deferred_signal, linux_resume_one_thread)
        (fetch_register, linux_write_memory, linux_enable_event_reporting)
        (linux_tracefork_grandchild, linux_test_for_tracefork)
        (linux_read_offsets, linux_xfer_siginfo, linux_xfer_siginfo ): Add
        PTRACE_ARG3_TYPE and PTRACE_ARG4_TYPE cast to ptrace arguments
        where the argument is 0.