Implement error recovery for directive tokens

[rynowak]

We're not strict enough with error detection for directive tokens - for example

@custom global::Some_Namespace

If the custom directive expects a namespace, it will parse the global token, and then fail because the ::Some_Namespace` token remains. If instead, another token was part of the directive that could consume this text, it was parse correctly.

So, that means that tokens are allowed to run together, and we don't prevent it today.

We also need to implement error recovery for tokens universally.