Allows custom Compare and Allocator on map-like data structures; reso… #496

Job	Run time
windows-msvc-shared (XML)	4m 1s
windows-msvc-shared (CAPNPROTO)	7m 43s
windows-msvc-shared (TOML)	4m 42s
windows-msvc-shared (JSON)	11m 11s
windows-msvc-shared (FLEXBUFFERS)	5m 30s
windows-msvc-shared (MSGPACK)	3m 55s
windows-msvc-shared (AVRO)	7m 28s
windows-msvc-shared (UBJSON)	7m 43s
windows-msvc-shared (CBOR)	8m 48s
windows-msvc-shared (PARQUET)	41m 54s
windows-msvc-shared (YAML)	4m 20s
windows-msvc (CBOR)	8m 31s
windows-msvc (FLEXBUFFERS)	5m 27s
windows-msvc (MSGPACK)	3m 51s
windows-msvc (YAML)	4m 53s
windows-msvc (TOML)	4m 55s
windows-msvc (PARQUET)	39m 45s
windows-msvc (AVRO)	6m 56s
windows-msvc (CAPNPROTO)	7m 54s
windows-msvc (JSON)	12m 6s
windows-msvc (XML)	4m 27s
windows-msvc (UBJSON)	6m 58s
windows-msvc (benchmarks)	46m 23s
	4h 19m 21s

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