Core/Instances: Implemented confirmation dialog for players upon entering instance which would permanently bind the player to it, players can now choose to get saved or leave the instance

Also fixes broken build

src/server/scripts/Northrend/IcecrownCitadel/instance_icecrown_citadel.cpp

@@ -395,6 +395,16 @@ class instance_icecrown_citadel : public InstanceMapScript
                  return true;
             }
 
+            uint32 GetCompletedEncounterMask() const
+            {
+                uint32 mask = 0;
+                for (uint8 i = 0; i < MAX_ENCOUNTER; ++i)
+                    if (GetBossState(i) == DONE)
+                        mask |= 1 << i;
+
+                return mask;
+            }
+
             void SetData(uint32 type, uint32 data)
             {
                 switch (type)