tools/libinput-replay: print a separator line for EV_SYN events

If running with --verbose having that line makes it a lot easier to
look at the event sequence.

Part-of: <https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/1094>

tools/libinput-replay.py

@@ -165,6 +165,10 @@ def print_events(devnode, indent, evs):
                 e.value,
             )
         )
+        if e.type == libevdev.EV_SYN:
+            print(
+                "{}: ------------------------------------------------".format(devnode)
+            )
 
 
 def collect_events(frame):