Add cmake + native windows support for asymptote, with fully working make support #19

Job	Run time
determine_version_suffix	8s
build-gui / build-gui-windows	43s
build-gui / build-gui-linux	11s
build-asy-windows / configure-windows-msvc-x64	1m 33s
build-asy-linux / configure-linux-release-x64	59s
build-asy-linux / build-linux-release-x64	1m 48s
build-asy-windows / build-windows-msvc-x64	6m 43s
build-asy-linux / linux-asy-docgen	2m 36s
build-asy-linux / package-asymptote-artifacts	6s
test-asy-linux / test-x64-cxxtests	28s
test-asy-linux / test-x64-asy-tests	50s
package-asy-install-file	0s
test-asy-windows / test-windows-msvc-x64-asy-tests	46s
test-asy-windows / test-windows-msvc-x64-cxxtests	27s
precheck-pass	0s
	17m 18s

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