Allow aliases with `using` #202

Job	Run time
determine_asy_version	8s
lint-non-gui-files / check-if-non-gui-py-files-changed	6s
lint-non-gui-files / lint-python-files	0s
build-asy-linux / configure-linux-release-x64	40s
build-gui / build-gui-linux	11s
build-asy-windows / configure-windows-msvc-x64	1m 52s
build-gui / build-gui-windows	45s
build-asy-linux / build-linux-release-x64	2m 2s
build-asy-windows / build-windows-msvc-x64	7m 31s
build-asy-linux / linux-asy-docgen	2m 31s
build-asy-linux / package-asymptote-artifacts	16s
test-asy-linux / test-x64-asy-tests	55s
test-asy-linux / test-x64-cxxtests	25s
package-asy-install-file / package-asy-installer	58s
test-asy-windows / test-windows-msvc-x64-cxxtests	41s
test-asy-windows / test-windows-msvc-x64-asy-tests	1m 59s
precheck-pass	1s
	21m 1s

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