Query cache is not used for tables or databases with dots in their names

I've confirmed this bug with mariadb 5.1.49 from our delta rep for lucid (5.1.49-mariadb82) it is not present on mysql 5.1.41 on lucid (5.1.41-3ubuntu12.6)

Can be replicated as follows

MariaDB [(none)]> CREATE DATABASE `foo.bar`;
Query OK, 1 row affected (0.00 sec)

MariaDB [(none)]> use foo.bar;
Database changed

MariaDB [foo.bar]> CREATE TABLE moocow (a int);
Query OK, 0 rows affected (0.01 sec)

MariaDB [foo.bar]> SHOW STATUS LIKE 'Qcache%';
+-------------------------+-----------+
| Variable_name | Value |
+-------------------------+-----------+
| Qcache_free_blocks | 1 |
| Qcache_free_memory | 268415928 |
| Qcache_hits | 1 |
| Qcache_inserts | 1 |
| Qcache_lowmem_prunes | 0 |
| Qcache_not_cached | 15311 |
| Qcache_queries_in_cache | 1 |
| Qcache_total_blocks | 4 |
+-------------------------+-----------+
8 rows in set (0.00 sec)

MariaDB [foo.bar]> INSERT INTO moocow VALUES (1), (2), (3);
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0

MariaDB [foo.bar]> SELECT * FROM moocow;
+------+
| a |
+------+
| 1 |
| 2 |
| 3 |
+------+
3 rows in set (0.00 sec)

MariaDB [foo.bar]> SHOW STATUS LIKE 'Qcache%';
+-------------------------+-----------+
| Variable_name | Value |
+-------------------------+-----------+
| Qcache_free_blocks | 1 |
| Qcache_free_memory | 268415928 |
| Qcache_hits | 1 |
| Qcache_inserts | 1 |
| Qcache_lowmem_prunes | 0 |
| Qcache_not_cached | 15312 |
| Qcache_queries_in_cache | 1 |
| Qcache_total_blocks | 4 |
+-------------------------+-----------+
8 rows in set (0.00 sec)