Fixed parsing of b'1', and ^A and ^@ for boolean values.

b'1' occurs in the dafault value for bit(1) fields.

(Latter was really done by https://github.com/cewing.)

MariaDB [test]> show create table bintest\G
*************************** 1. row ***************************
       Table: bintest
Create Table: CREATE TABLE `bintest` (
  `b` bit(1) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

MariaDB [test]> select * from bintest;
+------+
| b    |
+------+
|      |  -- zero, meaning false, prints as only spaces
|     | -- one, meaning true, prints as a single \x01
| NULL |  -- when the row is NULL
+------+
3 rows in set (0.00 sec)