PulseAudio: mark stream non-monotonic

In some cases, that gets more accurate timing meaurements faster.

VLC does not use pa_stream_get_time(), so there is certainly no need
for pa_stream_get_time() to return monotonic values.
(cherry picked from commit 44bf8bbcb3fbd1d6c04c2ed8eec27f75f8faf340)

modules/audio_output/pulse.c

@@ -822,6 +822,7 @@ static int Open(vlc_object_t *obj)
     /* Stream parameters */
     const pa_stream_flags_t flags = PA_STREAM_START_CORKED
                                   //| PA_STREAM_INTERPOLATE_TIMING
+                                    | PA_STREAM_NOT_MONOTONIC
                                   | PA_STREAM_AUTO_TIMING_UPDATE
                                   | PA_STREAM_VARIABLE_RATE;