Fix circular include on MS Visual Studio #3226

Job	Run time
clang-valgrind-intltest (utility)	6m 55s
clang-valgrind-test	10m 13s
clang-valgrind-intltest (normalize)	6m 6s
clang-valgrind-intltest (collator)	5m 21s
clang-valgrind-intltest (regex)	5m 30s
clang-valgrind-intltest (format)	16m 2s
clang-valgrind-intltest (translit)	6m 20s
clang-valgrind-intltest (rbbi)	8m 5s
clang-valgrind-intltest (rbnf)	6m 8s
clang-valgrind-intltest (rbnfrt)	6m 10s
clang-valgrind-intltest (icuserv)	5m 4s
clang-valgrind-intltest (idna)	5m 30s
clang-valgrind-intltest (convert)	6m 52s
clang-valgrind-intltest (rbnfp)	5m 26s
clang-valgrind-intltest (csdet)	5m 20s
clang-valgrind-intltest (spoof)	5m 22s
clang-valgrind-intltest (bidi)	5m 28s
	1h 55m 52s

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