Include struct layout in callbacks. #3009

Job	Run time
check-cfg	22s
docs	24s
msrv	48s
quickchecking	21s
rustfmt-clippy	30s
minimal	19s
test-expectations (ubuntu-latest)	47s
test-expectations (macos-latest)	54s
test-book	35s
test (ubuntu-latest, 9.0, 0, 0, 0, 0)	1m 43s
test-no-headers	24s
test (ubuntu-latest, 9.0, 0, 0, 1, 0)	1m 55s
test (ubuntu-latest, 9.0, 0, 1, 0, 0)	1m 39s
test (ubuntu-latest, 9.0, 0, 1, 1, 0)	1m 40s
test (ubuntu-latest, 9.0, 1, 0, 0, 0)	2m 10s
test (ubuntu-latest, 9.0, 1, 0, 1, 0)	2m 12s
test (ubuntu-latest, 9.0, 1, 1, 0, 0)	2m 11s
test (ubuntu-latest, 9.0, 1, 1, 1, 0)	2m 23s
test (ubuntu-latest, 16.0, 0, 0, 0, 0)	4m 18s
test (ubuntu-latest, 16.0, 0, 0, 1, 0)	4m 9s
test (ubuntu-latest, 16.0, 0, 1, 0, 0)	3m 59s
test (ubuntu-latest, 16.0, 0, 1, 1, 0)	4m 28s
test (ubuntu-latest, 16.0, 1, 0, 0, 0)	4m 58s
test (ubuntu-latest, 16.0, 1, 0, 1, 0)	4m 55s
test (ubuntu-latest, 16.0, 1, 1, 0, 0)	5m 1s
test (ubuntu-latest, 16.0, 1, 1, 1, 0)	5m 0s
test (ubuntu-latest, 16.0, 0, 0, 1)	2m 29s
test (macos-latest, 16.0, 0, 0, 0)	2m 20s
success	1s
	1h 2m 55s

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