Add OpenBSD support #381

Job	Run time
freebsd (test:unit)	7m 8s
freebsd (test:examples)	6m 0s
fedora (test:unit)	1m 25s
test-examples (ubuntu-latest, 3.1)	2m 24s
fedora (test:examples)	4m 7s
openbsd (test:unit)	21m 23s
test-examples (windows-latest, 3.1)	11m 9s
test-unit (ubuntu-latest, 2.3)	50s
openbsd (test:examples)	7m 36s
test-examples (macos-13, 3.1)	6m 44s
test-unit (ubuntu-latest, 2.4)	44s
test-unit (ubuntu-latest, 2.5)	53s
test-unit (ubuntu-latest, 2.6)	51s
test-unit (ubuntu-latest, 2.7)	50s
test-unit (ubuntu-latest, 3.0)	36s
test-unit (ubuntu-latest, 3.1)	1m 53s
test-unit (ubuntu-latest, 3.2)	42s
test-unit (ubuntu-latest, 3.3)	37s
test-unit (ubuntu-latest, head)	46s
test-unit (windows-latest, 2.3)	4m 4s
test-unit (windows-latest, 2.4)	3m 58s
test-unit (windows-latest, 2.5)	4m 55s
test-unit (windows-latest, 2.6)	5m 55s
test-unit (windows-latest, 2.7)	5m 11s
test-unit (windows-latest, 3.0)	3m 24s
test-unit (windows-latest, 3.1)	4m 6s
test-unit (windows-latest, 3.2)	4m 38s
test-unit (windows-latest, 3.3)	3m 46s
test-unit (windows-latest, head)	3m 17s
test-unit (macos-latest, 2.6)	46s
test-unit (macos-latest, 2.7)	48s
test-unit (macos-latest, 3.0)	32s
test-unit (macos-latest, 3.1)	31s
test-unit (macos-latest, 3.2)	33s
test-unit (macos-latest, 3.3)	34s
test-unit (macos-latest, head)	37s
	2h 4m 13s

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