Finish and polish new_game.c

Only one function is left undocumented. I tried to go into the assembly
to at least name it, but it clears fields in the save block that aren't
even documented yet.

include/field_specials.h

@@ -25,5 +25,7 @@ void UpdateFrontierManiac(u16 a0);
 void UpdateFrontierGambler(u16 a0);
 void ResetCyclingRoadChallengeData(void);
 bool8 warp0_in_pokecenter(void);
+void ResetFanClub(void);
+
 
 #endif // GUARD_FIELD_SPECIALS_H