avoid some C functions that are not in C99 #96

Job	Run time
ci (tpb, ubuntu-22.04, --pb --threads --enable-libffi, test-some-fast)	35m 57s
ci (a6osx, macos-12)	13m 57s
ci (ta6osx, macos-12)	17m 49s
ci (i3le, ubuntu-22.04)	12m 39s
ci (ti3le, ubuntu-22.04)	15m 52s
ci (a6le, ubuntu-22.04)	9m 0s
ci (ta6le, ubuntu-22.04)	12m 7s
ci (ta6le, ubuntu-22.04, reboot, -m=ta6le --force, re.boot SCHEME="chezscheme", test-some-fast)	8m 11s
ci (i3nt, windows-2022, vs)	11m 35s
ci (ti3nt, windows-2022, vs)	14m 47s
ci (a6nt, windows-2022, vs)	12m 25s
ci (ta6nt, windows-2022, vs)	15m 30s
ci (ta6nt, windows-2022, gcc)	12m 38s
	3h 12m 27s

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