Reduce overlay dependencies on global.h (7) (#2472)

* z64env_flags, z64quest_hint_commands

* z64cutscene_spline, z64save.h moved from z64.h

* bss

* pr suggestion

* bss

* suggestions

src/code/z_scene.c

@@ -1,6 +1,8 @@
 #include "global.h"
+#include "seqcmd.h"
 #include "terminal.h"
 #include "versions.h"
+#include "z64save.h"
 
 SceneCmdHandlerFunc sSceneCmdHandlers[SCENE_CMD_ID_MAX];
 RomFile sNaviQuestHintFiles[];