Document an includes style, apply to z_demo.c and z_play.c (#2803)

* Document an includes style, apply to z_demo.c and z_play.c

* "reverse" style includes

* bss

* clarify what a "main header" is

* Update docs/includes.md

Co-authored-by: Tharo <tharo10600@gmail.com>

* Update docs/includes.md

---------

Co-authored-by: Tharo <tharo10600@gmail.com>

include/actor.h

@@ -2,7 +2,7 @@
 #define ACTOR_H
 
 #include "color.h"
-#include "actor_profile.h"
+#include "actor_profile.h" // IWYU pragma: export
 #include "animation.h"
 #include "z_math.h"
 #include "collision_check.h"

include/dma.h

@@ -3,7 +3,7 @@
 
 #include "ultra64.h"
 #include "alignment.h"
-#include "romfile.h"
+#include "romfile.h" // IWYU pragma: export
 
 typedef struct DmaRequest {
     /* 0x00 */ uintptr_t    vromAddr; // VROM address (source)

include/transition.h

@@ -3,11 +3,14 @@
 
 #include "ultra64/ultratypes.h"
 #include "ultra64/gbi.h"
+
+// IWYU pragma: begin_exports
 #include "transition_circle.h"
 #include "transition_fade.h"
 #include "transition_triforce.h"
 #include "transition_wipe.h"
 #include "transition_instances.h"
+// IWYU pragma: end_exports
 
 #define TRANS_TRIGGER_OFF 0 // transition is not active
 #define TRANS_TRIGGER_START 20 // start transition (exiting an area)

include/ultra64.h

@@ -10,9 +10,10 @@
 #include "stdlib.h"
 #include "string.h"
 
-#include "ultra64/ultratypes.h"
+#include "ultra64/ultratypes.h" // IWYU pragma: export
 #include "unk.h"
 
+// IWYU pragma: begin_exports
 #include "ultra64/libc.h"
 #include "ultra64/xstdio.h"
 #include "ultra64/exception.h"
@@ -39,6 +40,7 @@
 #include "ultra64/siint.h"
 #include "ultra64/ucode.h"
 #include "ultra64/version.h"
+// IWYU pragma: end_exports
 
 union uObjBg;