Add support for utf8_unicode_ci

[renecannao]

Collation utf8_unicode_ci is currently not supported.

[renecannao]

This seems a but in MariaDB Client Connector C.
In MySQL:

mysql> SELECT * FROM INFORMATION_SCHEMA.COLLATIONS WHERE id IN (33,192);
+-----------------+--------------------+-----+------------+-------------+---------+
| COLLATION_NAME  | CHARACTER_SET_NAME | ID  | IS_DEFAULT | IS_COMPILED | SORTLEN |
+-----------------+--------------------+-----+------------+-------------+---------+
| utf8_general_ci | utf8               |  33 | Yes        | Yes         |       1 |
| utf8_unicode_ci | utf8               | 192 |            | Yes         |       8 |
+-----------------+--------------------+-----+------------+-------------+---------+
2 rows in set (0,00 sec)

In MariaDB Client Library:

$ grep _general_ci ./mariadb_client/libmariadb/my_charset.c  | grep UTF8_MB3
  {  33, 1, UTF8_MB3, UTF8_MB3"_general_ci", "", 65001, "UTF-8", 1, 3, mysql_mbcharlen_utf8mb3,  check_mb_utf8mb3_valid},
  { 192, 1, UTF8_MB3, UTF8_MB3"_general_ci", "", 65001, "UTF-8", 1, 3, mysql_mbcharlen_utf8mb3, check_mb_utf8mb3_valid},