- Added Threshold Manipulation.

- Added 'threshold' and 'defthreshold' to DECORATE expression exposure.
- ChaseThreshold sets the default threshold for how long a monster must chase one target before it can switch targets. Default is 100, must not be negative.
- A_SetChaseThreshold can be used to alter the current or default threshold of an actor <pointer>.
- Changing current threshold has no effect on what the default will be once it hits 0 and something makes it infight with another.

src/p_mobj.cpp

@@ -344,6 +344,10 @@ void AActor::Serialize (FArchive &arc)
 			<< RipLevelMin
 			<< RipLevelMax;
 	}
+	if (SaveVersion >= 4525)
+	{
+		arc << DefThreshold;
+	}
 
 	{
 		FString tagstr;