Parse error when hook to mock is contains special chars.

[gmazzap]

When mocking an hook that has special chars in names, e.g.

Filters::expectApplied( 'foo.bar' );

Test result is a parse error.

Reason is that internally Brain Monkey creates a Mockery mock using hook id, and Mockery creates a class using hook name as class name.

So, if the hook name is not valid as class name a parse error occurs.