Issue #12469: fix signal order check of test_signal
Issue #12469: fix signal order check of test_signal

When signals are unblocked, pending signal ared delivered in the reverse order
of their number (also on Linux, not only on FreeBSD 6).

Don't sort signals by their number if signals were not blocked (test_signum).

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator