Recognize inline namespaces using clang's dedicated API for that #2460

Job	Run time
check-cfg	23s
minimal	25s
msrv	51s
docs	21s
quickchecking	22s
rustfmt-clippy	29s
test-book	27s
test (ubuntu-latest, 9.0, 1, 0, 0, 0, 0)	2m 26s
test (ubuntu-latest, 9.0, 1, 0, 0, 1, 0)	3m 0s
test-expectations (ubuntu-latest)	44s
test-expectations (macos-12)	1m 8s
test (ubuntu-latest, 9.0, 1, 0, 1, 0, 0)	2m 11s
test (ubuntu-latest, 9.0, 1, 0, 1, 1, 0)	2m 2s
test (ubuntu-latest, 9.0, 1, 1, 0, 0, 0)	2m 30s
test (ubuntu-latest, 9.0, 1, 1, 0, 1, 0)	2m 27s
test (ubuntu-latest, 9.0, 1, 1, 1, 0, 0)	2m 50s
test (ubuntu-latest, 9.0, 1, 1, 1, 1, 0)	3m 28s
test (ubuntu-latest, 16.0, 1, 0, 0, 0, 0)	5m 20s
test (ubuntu-latest, 16.0, 1, 0, 0, 1, 0)	4m 31s
test (ubuntu-latest, 16.0, 1, 0, 1, 0, 0)	4m 31s
test (ubuntu-latest, 16.0, 1, 0, 1, 1, 0)	4m 0s
test (ubuntu-latest, 16.0, 1, 1, 0, 0, 0)	5m 39s
test (ubuntu-latest, 16.0, 1, 1, 0, 1, 0)	5m 55s
test (ubuntu-latest, 16.0, 1, 1, 1, 0, 0)	5m 28s
test (ubuntu-latest, 16.0, 1, 1, 1, 1, 0)	5m 11s
test (ubuntu-latest, 16.0, 0, 0, 1)	2m 47s
test (macos-12, 9.0, 0, 0, 0)	1m 35s
success	1s
	1h 11m 2s

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