[GH-166] Fixes a bug caused by unquoted reserved table name being referenced during schema creation

This issue is created automatically through a Github pull request on behalf of klaussilveira:

Url: https://github.com/doctrine/dbal/pull/166

Message:

When creating a schema with tables with reserved names and relationships between them, the schema creation tool failed to write valid SQL in MySQL due to unquoted table names. For example:

CREATE TABLE `Group` (id INT AUTO_INCREMENT NOT NULL, name VARCHAR(255) NOT NULL DEFAULT NULL, PRIMARY KEY(id)) ENGINE = InnoDB;
CREATE TABLE User (id INT AUTO_INCREMENT NOT NULL, username VARCHAR(255) NOT NULL PRIMARY KEY(id)) ENGINE = InnoDB;
CREATE TABLE UserHasGroup (user_id INT NOT NULL, group_id INT NOT NULL, INDEX IDX_617A865CA76ED395 (user_id), INDEX IDX_617A865CFE54D947 (group_id), PRIMARY KEY(user_id, group_id)) ENGINE = InnoDB;
ALTER TABLE UserHasGroup ADD CONSTRAINT FK_617A865CA76ED395 FOREIGN KEY (user_id) REFERENCES User (id);
ALTER TABLE UserHasGroup ADD CONSTRAINT FK_617A865CFE54D947 FOREIGN KEY (group_id) REFERENCES Group (id);

This fix creates a small function for creating quoted foreign key table names.