PassedParameters: allow for parsing declare statements

[jrfnl]

From #339 (comment):

The only thing from the above thread which I think might be interesting for PHPCSUtils could be to offer a function to parse declare statements into the individual directives, returning an array of arrays with directive, directive_token, value, value_token (or something along those lines).

This could help standards which examine declare statements to handle multi-directive statements correctly.

Then again, it may be better/more straight-forward to add T_DECLARE to the list of tokens parsable by the PassedParameters class (and ensure that it is supported correctly) ?