Use MRB_DUMP_SIZE_OF_CHAR instead of sizeof(char).

include/mruby/dump.h

@@ -41,6 +41,7 @@ int mrb_bdump_irep(mrb_state *mrb, int n, FILE *f,const char *initname);
 #define MRB_DUMP_SIZE_OF_LONG          4
 #define MRB_DUMP_SIZE_OF_INT           4
 #define MRB_DUMP_SIZE_OF_SHORT         2
+#define MRB_DUMP_SIZE_OF_CHAR          1
 
 /* null symbol length */
 #define MRB_DUMP_NULL_SYM_LEN          0xFFFF

src/dump.c

@@ -84,7 +84,7 @@ uint8_dump(unsigned char bin, char *hex, int type)
     *hex++  = bin2hex[(bin >> 4) & 0x0f];
     *hex    = bin2hex[bin & 0x0f];
   }
-  return DUMP_SIZE(sizeof(char), type);
+  return DUMP_SIZE(MRB_DUMP_SIZE_OF_CHAR, type);
 }
 
 static inline int