…nthesis

Code:
```php
$anonClass = new class($arg) {};
```

As anonymous classes have a distinct token, it makes sense to me to assign that token as the parenthesis owner, along the same lines as is done for anonymous functions.

The main difference is that for anonymous classes, the parenthesis are optional.

Assigning an owner for them can not be done from within the `Tokenizer::createTokenMap()` as at that point in time the `PHP::processAdditional()` method hasn't run yet, so the token is still a `T_CLASS`.

It can however be adjusted from within the `PHP::processAdditional()` method when the `T_CLASS` token is changed to a `T_ANON_CLASS` token.

This commit implements this.

This means that for the `class` token in the above code snippet will now have a `parenthesis_owner`, `parenthesis_opener` and `parenthesis_closer` in the `$tokens` array.
The parenthesis opener and closer will both now also have the `parenthesis_owner` key, in addition to the `parenthesis_opener` and `parenthesis_closer` keys which they already had.

Instead of testing this via existing sniffs, I have chosen to add a new set of `Core` tests for specific tokenizer issues, with the tests for this change being the first set of tests added.

Includes:
* Adding the `T_ANON_CLASS` token to the `Tokens::$parenthesisOpeners` array.
* Removing the `T_ANON_CLASS` from the "additional tokens indicating that parenthesis are not arbitrary" list in the `Generic.WhiteSpace.ArbitraryParenthesesSpacing` sniff.