[PHP7] Possible class initialization bug

Hej,

I tried hxBit lib and especially the serializer, and I get an exception from hxBit "Too late to register Class" that occurs when a class try to register itself in the Serializer. This registration is called in `static public function __hx__init`. (a macro injects that).
When I run the serializer, it calls `__hx__init` when it meet a new class that need to be serialized, but once it's running it's "Too late to register Class".
So in order to make it work, I have to call these classes once by hand before running the hxBit serializer.

@ncannasse : I don't really know if it's a PHP7 plateform's issue or if it's a hxBit behaviour.