More minor isolated fixes (#1258)

* Fix reversed array access in z_boss_dodongo.c

* Remove useless return in z_en_encount2.c

* Remove some redundant externs or declarations

* Move some undefs to be performed as early as possible

* AudioOcarina_ResetStaffs -> AudioOcarina_ResetStaves

The plural appears to be staves for the music term

* Remove some uses of UNK_PTR

* Use NULL for pointers set to 0 in z_game_dlftbls.c

* Remove useless !! in z_en_tk.c

* Revert "AudioOcarina_ResetStaffs -> AudioOcarina_ResetStaves"

This reverts commit 1b7fe62408.

* Remove more redundant externs from PR suggestion

src/code/code_800EC960.c

@@ -2297,12 +2297,6 @@ f32 D_80131C8C = 0.0f;
 
 // =========== Audio Debugging ===========
 
-extern u16 gAudioSfxSwapSource[];
-extern u16 gAudioSfxSwapTarget[];
-extern u8 gAudioSfxSwapMode[];
-extern u8 gAudioSfxSwapOff;
-extern u8 D_801333F0;
-
 u32 sDebugPadHold;
 u32 sDebugPadBtnLast;
 u32 sDebugPadPress;

src/code/z_game_dlftbls.c

@@ -3,10 +3,10 @@
 #define GAMESTATE_OVERLAY(name, init, destroy, size)                                                         \
     {                                                                                                        \
         NULL, (u32)_ovl_##name##SegmentRomStart, (u32)_ovl_##name##SegmentRomEnd, _ovl_##name##SegmentStart, \
-            _ovl_##name##SegmentEnd, 0, init, destroy, 0, 0, 0, size                                         \
+            _ovl_##name##SegmentEnd, NULL, init, destroy, NULL, NULL, 0, size                                \
     }
 #define GAMESTATE_OVERLAY_INTERNAL(init, destroy, size) \
-    { NULL, 0, 0, NULL, NULL, 0, init, destroy, 0, 0, 0, size }
+    { NULL, 0, 0, NULL, NULL, NULL, init, destroy, NULL, NULL, 0, size }
 
 GameStateOverlay gGameStateOverlayTable[] = {
     GAMESTATE_OVERLAY_INTERNAL(TitleSetup_Init, TitleSetup_Destroy, sizeof(GameState)),

src/code/z_skelanime.c

@@ -9,8 +9,6 @@ s32 SkelAnime_LoopFull(SkelAnime* skelAnime);
 s32 SkelAnime_Once(SkelAnime* skelAnime);
 s32 SkelAnime_LoopPartial(SkelAnime* skelAnime);
 
-void SkelAnime_CopyFrameTable(SkelAnime* skelAnime, Vec3s* dst, Vec3s* src);
-
 static u32 sDisableAnimQueueFlags = 0;
 static u32 sAnimQueueFlags;