testsuite: Fix runaway attach processes

testsuite: Fix runaway attach processes

I have started seeing occasional runaway 'attach' processes these days.
I cannot be certain it is really caused by this patch, for example
grep 'FAIL.*cmdline attach run' does not show anything in my logs.

But as I remember this 'attach' runaway process always happened in GDB (but
I do not remember it in the past months) I think it would be most safe to just
solve it forever by [attached].

gdb/testsuite/ChangeLog
2014-09-12  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.base/attach.c: Include unistd.h.
	(main): Call alarm.  Add label postloop.
	* gdb.base/attach.exp (do_attach_tests): Use gdb_get_line_number,
	gdb_breakpoint, gdb_continue_to_breakpoint.
	(test_command_line_attach_run): Kill ${testpid} in one exit path.