readint.c: fixed typo.
/* mrb_int_read(): read mrb_int from a string (base 10 only) */
/* const char *p - string to read */
/* const char *e - end of string */
-/* char **endp - end of pased integer */
+/* char **endp - end of parsed integer */
/* if integer overflows, errno will be set to ERANGE */
/* also endp will be set to NULL on overflow */
