Removing C++17 standard library stuff #296

Job	Run time
test (d2q9, float, same, true)	5m 8s
test (d2q9, float, same, false)	5m 57s
test (d2q9, float, half, true)	5m 9s
test (d2q9, float, half-shift, true)	4m 59s
test (d2q9, float, float, true)	5m 12s
test (d2q9, float, float, false)	4m 51s
test (d2q9, float, float-shift, true)	5m 0s
test (d2q9, float, float-shift, false)	4m 54s
test (d2q9, double, same, true)	5m 28s
test (d2q9, double, same, false)	4m 53s
test (d2q9, double, half, true)	4m 57s
test (d2q9, double, half-shift, true)	5m 7s
test (d2q9, double, float, true)	5m 7s
test (d2q9, double, float, false)	4m 47s
test (d2q9, double, float-shift, true)	5m 6s
test (d2q9, double, float-shift, false)	4m 41s
test (d2q9, double, double, true)	5m 14s
test (d2q9, double, double, false)	4m 58s
	1h 31m 28s

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