* linux-low.c (linux_kill_one_lwp, linux_kill)
(linux_detach_one_lwp): Adjust to send_sigstop interface change.
(send_sigstop): Take an lwp_info as parameter instead. Queue a
SIGSTOP even if the LWP is stopped.
(send_sigstop_callback): New.
(stop_all_lwps): Use send_sigstop_callback instead.
(linux_resume_one_thread): Adjust.
(proceed_one_lwp): Still proceed an LWP that the client has
requested to stop, if we haven't reported it as stopped yet. Make
sure that LWPs the client want stopped, have a pending SIGSTOP.