test

Make persist compatible with C++17 #466

Job	Run time
build	16m 57s
build-spm	17s
docs	1m 8s
check (Debug, gnu-6, 14)	2m 58s
check (Debug, gnu-7, 14)	3m 7s
check (Debug, llvm-5, 14)	2m 37s
check (Debug, llvm-6, 14)	2m 39s
check (Release, gnu-6, 14)	3m 44s
check (Release, gnu-7, 14)	3m 50s
check (Release, llvm-5, 14)	4m 5s
check (Release, llvm-6, 14)	4m 23s
check (Debug, gnu-9, 14, coverage)	4m 5s
check (Debug, gnu-8, 17)	3m 10s
check (Debug, llvm-9, 17, fuzzers)	4m 7s
check (Debug, gnu-11, 20)	3m 34s
check (Debug, llvm-13, 20)	3m 20s
check (Debug, llvm-8, 14, sanitize)	3m 55s
check (Release, gnu-9, 14, benchmark)	18m 40s
check (Release, llvm-10, 14, benchmark)	18m 57s
	1h 45m 33s

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