Allow support for atomic variables; resolves #575 #442

Job	Run time
windows-msvc-shared (CBOR)	8m 39s
windows-msvc-shared (MSGPACK)	3m 47s
windows-msvc-shared (CAPNPROTO)	8m 0s
windows-msvc-shared (FLEXBUFFERS)	5m 37s
windows-msvc-shared (TOML)	4m 12s
windows-msvc-shared (JSON)	10m 36s
windows-msvc-shared (UBJSON)	7m 22s
windows-msvc-shared (AVRO)	7m 1s
windows-msvc-shared (YAML)	4m 11s
windows-msvc-shared (XML)	5m 24s
windows-msvc-shared (PARQUET)	41m 1s
windows-msvc (YAML)	4m 13s
windows-msvc (JSON)	10m 59s
windows-msvc (benchmarks)	47m 54s
windows-msvc (CBOR)	8m 15s
windows-msvc (UBJSON)	7m 25s
windows-msvc (XML)	3m 52s
windows-msvc (CAPNPROTO)	7m 44s
windows-msvc (TOML)	3m 51s
windows-msvc (FLEXBUFFERS)	6m 52s
windows-msvc (AVRO)	7m 23s
windows-msvc (MSGPACK)	4m 10s
windows-msvc (PARQUET)	41m 18s
	4h 19m 46s

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