• Change booleans interop logic (again) for JSON-XS-3.01
  Check now for Types::Serialiser::Boolean ie JSON::PP::Boolean refs (#18 clintongormley)
  to avoid allow_blessed for JSON-XS-3.01 booleans.
  
• fix boolean representation for JSON-XS-3.01/Types::Serialiser::Boolean interop
  (arrayref, not hashref)
  
• add t/52_object.t from JSON::XS
  
• backport encode_hv HE sort on stack < 64 or heap to avoid stack
  overflows from JSON-XS-3.01. do not use alloca.
  
• backport allow_tags, decode_tag, FREEZE/THAW callbacks from JSON-XS-3.01
  
• added pod for OBJECT SERIALISATION (allow_tags, FREEZE/THAW)