Fix isInfixOf and breakSubString in Word16 #179

Job	Run time
i386	7m 38s
darwin_arm (self-hosted, macOS, ARM64, 8.10.7)	13m 49s
darwin_arm (self-hosted, macOS, ARM64, 9.2.6)	8m 46s
darwin_arm (self-hosted, macOS, ARM64, 9.4.4)	10m 10s
build (ubuntu-latest, 8.0.2, 3.8.1.0)	14m 46s
build (ubuntu-latest, 8.2.2, 3.8.1.0)	7m 56s
build (ubuntu-latest, 8.4.4, 3.8.1.0)	9m 52s
build (ubuntu-latest, 8.6.5, 3.8.1.0)	7m 30s
build (ubuntu-latest, 8.8.4, 3.8.1.0)	6m 39s
build (ubuntu-latest, 8.10.7, 3.8.1.0)	6m 42s
build (ubuntu-latest, 9.0.2, 3.8.1.0)	6m 35s
build (ubuntu-latest, 9.2.7, 3.8.1.0)	5m 16s
build (ubuntu-latest, 9.4.5, 3.8.1.0)	8m 18s
build (ubuntu-latest, 9.6.1, 3.8.1.0)	5m 57s
build (macOS-latest, 9.4.5, 3.8.1.0)	9m 58s
build (macOS-latest, 9.6.1, 3.8.1.0)	12m 54s
build (windows-latest, 9.4.5, 3.8.1.0)	16m 6s
build (windows-latest, 9.6.1, 3.8.1.0)	18m 50s
arm (arm32v7)	4m 33s
arm (arm64v8)	3m 29s
	3h 5m 44s

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