Treats # as a delimited in R6RS mode when reading numbers (fixes #687) #419

Job	Run time
ci (tpb, ubuntu-22.04, --pb --threads --enable-libffi, test-some-fast)	30m 3s
ci (a6osx, macos-13)	15m 52s
ci (ta6osx, macos-13)	24m 56s
ci (arm64osx, macos-14)	9m 14s
ci (tarm64osx, macos-14)	11m 6s
ci (i3le, ubuntu-22.04)	12m 39s
ci (ti3le, ubuntu-22.04)	15m 59s
ci (a6le, ubuntu-22.04)	10m 3s
ci (ta6le, ubuntu-22.04, CFLAGS+=-std=gnu89)	12m 5s
ci (ta6le, ubuntu-22.04, reboot, -m=ta6le --force, re.boot SCHEME="chezscheme", test-some-fast)	8m 12s
ci (i3nt, windows-2022, vs)	11m 59s
ci (ti3nt, windows-2022, vs)	14m 39s
ci (a6nt, windows-2022, vs)	11m 50s
ci (ta6nt, windows-2022, vs)	14m 55s
ci (ta6nt, windows-2022, gcc, CFLAGS+=-std=gnu89)	12m 57s
ci (ta6le, ubuntu-22.04, test-more, more)	58m 26s
	4h 34m 55s

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