The 'r' encoding for unserialization was broken for collections because the
code was calling Variant::unserialize() on a temporary Variant, which is a
no-no. unserialize() must be called directly on the value where it resides
in the collection.
Second, there was an inconsistency between serialize and unserialize with
how id numbers worked for the 'r' and 'R' encodings. This diff fixes
serialize and unserialize to count collection keys when assigning id
numbers. I also took the opportunity to tighten up enforcement to prevent
collections keys and values from being taken by reference when during
unserialization.
This change is mostly for FB internal organizational reasons.
Building is not effected beyond the fact that the target now
lands in hphp/hhvm/hhvm rather than src/hhvm/hhvm.
andrewparoski