monitor: log INFO when for-plugins StartUp event synthesized

This is actually to do with a reported issue around the ctypes code in
`EDLogs.gamerunning()` causing:

```python
exception ignored on calling ctypes callback function: <function EDLogs.game_running.<locals>.callback at 0x0000020E9C9D0EA0>
Traceback (most recent call last):
  File "monitor.pyc", line 2041, in callback
  File "monitor.pyc", line 2034, in WindowTitle
ctypes.ArgumentError: argument 1: OverflowError: int too long to convert
```

Although I can't personally get this to trigger at all under 64-bit python,
either in PyCharm *or* with the 5.7.1-alpha1 64-bit pre-release.

`game_running()` is only used in a few places, and the key things it
malfunctioning might cause are lack of the synthetic `ShutDown` (already
has an INFO logging) and `StartUp` events.

monitor.py

@@ -415,6 +415,7 @@ class EDLogs(FileSystemEventHandler):  # type: ignore # See below
 
         if self.live:
             if self.game_was_running:
+                logger.info("Game is/was running, so synthesizing StartUp event for plugins")
                 # Game is running locally
                 entry: OrderedDictT[str, Any] = OrderedDict([
                     ('timestamp', strftime('%Y-%m-%dT%H:%M:%SZ', gmtime())),