Check whether files could be opened before writing; resolves #542 (#555) #389

Job	Run time
windows-msvc-shared (AVRO)	7m 2s
windows-msvc-shared (CBOR)	9m 11s
windows-msvc-shared (JSON)	10m 41s
windows-msvc-shared (CAPNPROTO)	8m 6s
windows-msvc-shared (PARQUET)	39m 24s
windows-msvc-shared (UBJSON)	7m 6s
windows-msvc-shared (MSGPACK)	3m 54s
windows-msvc-shared (FLEXBUFFERS)	5m 55s
windows-msvc-shared (TOML)	4m 19s
windows-msvc-shared (XML)	3m 44s
windows-msvc-shared (YAML)	4m 18s
windows-msvc (CBOR)	8m 32s
windows-msvc (TOML)	4m 15s
windows-msvc (XML)	3m 50s
windows-msvc (YAML)	4m 7s
windows-msvc (benchmarks)	48m 19s
windows-msvc (JSON)	10m 40s
windows-msvc (FLEXBUFFERS)	5m 43s
windows-msvc (MSGPACK)	4m 45s
windows-msvc (UBJSON)	7m 24s
windows-msvc (AVRO)	6m 50s
windows-msvc (CAPNPROTO)	7m 59s
windows-msvc (PARQUET)	39m 41s
	4h 15m 45s

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