ReservedFunctionNames: ignore deprecated methods by design

Functions and methods should not use a double underscore prefix in the function name as all functions and methods with that prefix are reserved by PHP Core.

When a (public/protected) method/function is renamed, however, it breaks backward-compatibility, so it is common to deprecate the old method name and add a new method with a name which does comply.

I'm proposing that if a function/method is marked as deprecated in the function docblock, that the sniff should not throw an error.

class Example {
    public function newName() {
    }

    /**
     * @deprecated x.x.x Use Example::new_Name() instead.
     */
    public function __oldName() {
        return self::newName();
    }
}

Currently the sniff would throw an error for the __oldName() method. Once this enhancement has been implemented, it no longer should.