primary key on MySQL platform.

Default isolation level on mysql is REPEATABLE READ

https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_tx_isolation

[DBAL-2546] Fixed the failure of `Functional\StatementTest::testReuseStatementWithParameterBoundByReference()` on ibm_db2

The test is partially skipped due to:

1. Fetching blob as binary string from pdo_sqlsrv requires using `PDOStatement::bindColumn()` and `PDOStatement::fetch(PDO::FETCH_BIND)` which are not supported by the DBAL.
2. Setting encoding on the connection level is not supported: https://msdn.microsoft.com/en-us/library/ff628164(v=sql.105).aspx

The current driver has no option to allow the usage of SSL connections on mysql. I've used the same name params as mysql client.
An example of mysql client usage would be:

mysql --ssl-ca='path_to_ca.pem' --ssl-cert='path_to_client_cert.pem' --ssl-key='path_to_client_key.pem'

refactor secure connection as params

remove space

add space

refactor secure connection

rename method

rename method

docs: add ssl params to use in mysqli driver

rename test method

refactor method setSecureConnection

fix bug

add comment to method

remove string escaping