LynxOS: Resume the same thread when receiving a thread create/exit event.

LynxOS: Resume the same thread when receiving a thread create/exit event.

Before this patch, the ptid passed to lynx_resume was completely
ignored, and we used the current_inferior. This resulted in trying
to resume the inferior execution using the wrong ptid after having
received a thread create/exit event, because the inferior_ptid
was still set to the ptid prior to receiving the signal.

gdb/gdbserver/ChangeLog:

        * lynx-low.c (lynx_resume): Use the resume_info parameter
        to determine the ptid for the lynx_ptrace call, unless
        it is equal to minus_one_ptid, in which case we use the
        ptid of the current_inferior.
        (lynx_wait_1): After having received a thread create/exit
        event, resume the inferior's execution using the signaling
        thread's ptid, rather than the old ptid.