HttT S12 Fix bug: Divide by zero

An off-by-one on the turn calculations. Turns left should include current turn; else divides by zero on the last turn. To reproduce you MUST step through every turn! Simply jumping to the last turn or two will not tickle the bug.

data/campaigns/Heir_To_The_Throne/scenarios/12_Northern_Winter.cfg

@@ -5,12 +5,14 @@
     map_data="{campaigns/Heir_To_The_Throne/maps/12_Northern_Winter.map}"
 
     {TURNS 50 40 40}
-    # when changing the turn limits, also change this event accordingly
     [event]
         name=prestart
+        [store_turns]
+            variable=turn_limit
+        [/store_turns]
         [set_variable]
             name=turn_limit
-            {QUANTITY value 50 40 40}
+            add=1
         [/set_variable]
     [/event]