Update document for `MRB_USE_CUSTOM_RO_DATA_P`
MODIFY
doc/guides/mrbconf.md
doc/guides/mrbconf.md
@@ -146,6 +146,13 @@ largest value of required alignment.
* Uses `_etext` and `_edata`.
* It must be `_etext < data_addr < _edata`.
+`MRB_USE_CUSTOM_RO_DATA_P`
+* Takes precedence over `MRB_USE_ETEXT_EDATA`.
+* Please try if both `MRB_USE_ETEXT_EDATA` and `MRB_NO_INIT_ARRAY_START` are not available.
+* The `mrb_ro_data_p()` function is implemented by the user in an arbitrary file.
+* The prototype declaration is `mrb_bool mrb_ro_data_p(const char *ptr)`.
+* Return `TRUE` if `ptr` is in read-only section, otherwise return `FALSE`.
+
## Other configuration.
`MRB_UTF8_STRING`
* Adds UTF-8 encoding support to character-oriented String instance methods.

MODIFY
include/mrbconf.h
include/mrbconf.h
effective only when MRB_USE_ETEXT_EDATA is defined */
//#define MRB_NO_INIT_ARRAY_START
+/* if do not works both MRB_USE_ETEXT_EDATA and MRB_NO_INIT_ARRAY_START,
+ you can try mrb_ro_data_p() that you have implemented yourself in any file;
+ prototype is `mrb_bool mrb_ro_data_p(const char *ptr)` */
+//#define MRB_USE_CUSTOM_RO_DATA_P
+
/* turn off generational GC by default */
//#define MRB_GC_TURN_OFF_GENERATIONAL

Update document for `MRB_USE_CUSTOM_RO_DATA_P`