[Server] Add OnMpNumIncrement() script callback

apps/openmw-mp/Networking.cpp

@@ -303,6 +303,7 @@ void Networking::setCurrentMpNum(int value)
 int Networking::getNextMpNum()
 {
     currentMpNum++;
+    Script::Call<Script::CallbackIdentity("OnMpNumIncrement")>(currentMpNum);
     return currentMpNum;
 }
 

apps/openmw-mp/Script/ScriptFunctions.hpp

@@ -130,7 +130,8 @@ public:
             {"OnContainer",              Function<void, unsigned short, const char*>()},
             {"OnPlayerSendMessage",      Function<bool, unsigned short, const char*>()},
             {"OnPlayerEndCharGen",       Function<void, unsigned short>()},
-            {"OnGUIAction",              Function<void, unsigned short, int, const char*>()}
+            {"OnGUIAction",              Function<void, unsigned short, int, const char*>()},
+            {"OnMpNumIncrement",         Function<void, int>()}
     };
 };