remove gratuituous c++ dependency

cdblock.h

@@ -1,3 +1,5 @@
+#pragma once
+
 #include "type.h"
 
 struct cr_rr {

scsp.h

@@ -1,3 +1,5 @@
+#pragma once
+
 #include "type.h"
 
 // Because the main CPU cannot access in units of 8 bits, so read and write in

scu.h

@@ -1,3 +1,5 @@
+#pragma once
+
 #include "type.h"
 
 typedef struct scu_reg {

sh2.h

@@ -2,8 +2,6 @@
 
 #include "type.h"
 
-#include <cstddef>
-
 typedef struct sh2_reg {
   reg8 SMR;      // 0x000
   reg8 BRR;      // 0x001

smpc.h

@@ -1,3 +1,5 @@
+#pragma once
+
 #include "type.h"
 
 struct ioreg {

type.h

@@ -1,8 +1,8 @@
+#include <stddef.h>
 #include <stdint.h>
 
 #ifndef __cplusplus
 #define static_assert _Static_assert
-#define offsetof __builtin_offsetof
 #endif
 
 typedef volatile uint8_t reg8;

vdp1.h

@@ -1,3 +1,5 @@
+#pragma once
+
 #include "type.h"
 
 /* command table */

vdp2.h

@@ -1,3 +1,5 @@
+#pragma once
+
 #include "type.h"
 
 /* memory offsets */