Add namespace register. #15

Job	Run time
build-and-test (x86_64-unknown-linux-gnu, stable)	5m 55s
build-and-test (x86_64-unknown-linux-gnu, nightly)	5m 45s
build-and-test (x86_64-apple-darwin, stable)	7m 18s
build-and-test (x86_64-apple-darwin, nightly)	4m 37s
build-and-test (aarch64-apple-darwin, stable)	4m 36s
build-and-test (aarch64-apple-darwin, nightly)	5m 37s
build-and-test (x86_64-pc-windows-gnu, stable)	14m 26s
build-and-test (x86_64-pc-windows-gnu, nightly)	13m 27s
build-and-test (i686-pc-windows-gnu, stable)	13m 45s
build-and-test (i686-pc-windows-gnu, nightly)	15m 33s
build-and-test (x86_64-pc-windows-msvc, stable)	13m 57s
build-and-test (x86_64-pc-windows-msvc, nightly)	13m 19s
build-and-test (i686-pc-windows-msvc, stable)	23m 14s
build-and-test (i686-pc-windows-msvc, nightly)	14m 27s
	2h 35m 56s

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