Resolve externed prototypes in C files

include/quest_log.h

@@ -46,6 +46,7 @@ void sub_811231C(void);
 void sub_81139BC(void);
 void *QuestLogGetFlagOrVarPtr(bool8 isFlag, u16 idx);
 void QuestLogSetFlagOrVar(bool8 isFlag, u16 idx, u16 value);
+void sub_8110840(void *oldSave);
 
 extern u8 gUnknown_203ADFA;