Add comment for get_environ_ptr why this API is in stdlib.h
@@ -190,6 +190,8 @@ int rand(void);
/**
* @ingroup STDLIB_LIBC
* @brief Return a pointer to the thread specific environ variable
+ * @details This API is not a standard API. But another APIs which are related to ENV are in Stdlib,
+ * so this API is in Stdlib for ease.
* @param[in] A pointer to notify a size of environ variable
* @return A pointer to the current thread environ variable
* @since Tizen RT v1.0
