Add make_child() method to shared_buf_ref_t
buffer-backed objects and arrays. (still buggy)
Merge branch 'daniel_buf_ref_datum' into daniel_buf_ref_datum_2
Bug fixes
Initialize serialized type to satisfy GCC
Typo
Fixed datum_t::write_to_protobuf
Avoid some string copying when converting to protobuf / JSON
Efficient re-serialization of buffer-backed datums (handling of array size errors still missing)
Restore error checking when serializing datums to disk
Update comment about array serialization size
Merge branch 'daniel_buf_ref_datum' into daniel_buf_ref_datum_2
Merge branch 'daniel_buf_ref_datum' into daniel_buf_ref_datum_2

Conflicts:
	src/rdb_protocol/datum.cc
Merge branch 'daniel_buf_ref_datum' into daniel_buf_ref_datum_2

Conflicts:
	src/rdb_protocol/datum.cc
Refactored datum object/array serialization
Merge branch 'next' into daniel_buf_ref_datum_2

Conflicts:
	src/rdb_protocol/datum.cc
Merge branch 'next' into daniel_buf_ref_datum_2
Fix compilation on GCC 4.8
Add "is_range_interesting()" callback filter to depth_first_traversal.
Clarified comment