Remove old PHP6 forward compatibility

Howdy Back when PHP6 was actually a thing, we added the 'b' string literal prefix and the (binary) cast to be forward compatible with PHP6, however since the entire unicode strings part were dropped, these are no longer needed. I think its safe to remove these 2, and take it as a lession learned, to safely and selectively added forward compatibile features. Is there any objections against these? Ps, we do actually have docs[1] for these, explaining users they were added in 5.2.1, although after a brief search I did not find any common libraries and projects using either of these features. [1] http://php.net/manual/en/language.types.type-juggling.php -- regards, Kalle Sommer Nielsen kalle@php.net