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.
Replace "collection" with "collections" in various file names since
we typically use the plural form in conversation and documentation.
Add set() and removeAt() methods needed for collection interfaces. Also
add the KeyedIterable and KeyedIterator interfaces.
Add __construct() methods for collections
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.
mwilliams