[5.4] Added compileLock method to SqlServerGrammar.

[SebastianBerc]

In SQL Server:

$builder->select('*')->from('foo')->where('bar', '=', 'baz')->lock('with(holdlock)');

will generate SQL:

'select * from [foo] with(holdlock) where [bar] = ? with(holdlock)'

because a lock is added in the compileFrom method and overriding the compileLock method doesn't exist.