Use target_terminal_ours_for_output in infcmd.c

Use target_terminal_ours_for_output in infcmd.c

We're only doing output here, so leave raw/cooked mode alone, as well
as the SIGINT handler.

No need to restore terminal settings, we'll set inferior modes on the
following resume.

gdb/ChangeLog:
2016-04-12  Pedro Alves  <palves@redhat.com>

	* infcmd.c (post_create_inferior, prepare_one_step): Use
	target_terminal_ours_for_output instead of target_terminal_ours.