Moved all value type fields to the front of the BV struct, so that the reference types can grow to the end, as needed.
Moved all value type fields to the front of the BV struct, so that the reference types can grow to the end, as needed.

This should alleviate the need for separate x86 / x64 builds.  (re: issue #48)

hnafar/IronJS,xamarin/IronJS,hnafar/IronJS,fholm/IronJS,hnafar/IronJS,hnafar/IronJS,fholm/IronJS,fholm/IronJS,fholm/IronJS,hnafar/IronJS,xamarin/IronJS,xamarin/IronJS,xamarin/IronJS