Fix database-level permission bug by escaping slashes in db names

Hi,
my INFORMATION_SCHEMA.SCHEMA_PRIVILEGES table contains entries with table names such as 
```
usr\_web121\_7
```

However, db-level permissions won't work for me unless I ensure that slashes get escaped before passing the database name (TABLE_SCHEMA column) to REGEXP.

I'm not sure whether this is a phpMyAdmin bug or even a MySQL bug itself.


Server version: 5.5.31-0+wheezy1 - (Debian)
phpMyAdmin Version: 4.1.6