the new PID.
(unstopped_p, linux_signal_pid): Remove.
(linux_target_ops): Remove linux_signal_pid.
* remote-utils.c (putpkt, input_interrupt): Use signal_pid
global instead of target method.
* target.h (struct target_ops): Remove signal_pid. Update comment
for create_inferior.
* server.c (signal_pid): New variable.
(create_inferior): Set signal_pid. Block SIGTTOU and SIGTTIN in
gdbserver. Set the child to be the foreground process group.
(attach_inferior): Set signal_pid.
