Added rfl::DefaultVal, resolves #534 #364

Job	Run time
windows-msvc-shared (MSGPACK)	2m 40s
windows-msvc-shared (JSON)	2m 1s
windows-msvc-shared (AVRO)	3m 16s
windows-msvc-shared (FLEXBUFFERS)	4m 53s
windows-msvc-shared (TOML)	2m 20s
windows-msvc-shared (CBOR)	2m 3s
windows-msvc-shared (YAML)	2m 27s
windows-msvc-shared (XML)	2m 27s
windows-msvc-shared (CAPNPROTO)	4m 22s
windows-msvc-shared (UBJSON)	3m 2s
windows-msvc-shared (PARQUET)	36m 34s
windows-msvc (CBOR)	2m 4s
windows-msvc (CAPNPROTO)	4m 18s
windows-msvc (TOML)	2m 46s
windows-msvc (UBJSON)	2m 6s
windows-msvc (PARQUET)	36m 36s
windows-msvc (AVRO)	3m 8s
windows-msvc (benchmarks)	41m 50s
windows-msvc (FLEXBUFFERS)	4m 7s
windows-msvc (YAML)	2m 31s
windows-msvc (XML)	2m 11s
windows-msvc (MSGPACK)	2m 7s
windows-msvc (JSON)	1m 59s
	2h 51m 48s

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