test-unlinkat: enhance test, to expose Solaris 9 bug Share the unlink tests with unlinkat. * tests/test-unlink.c (main): Factor guts... * tests/test-unlink.h (test_rmdir_func): ...into new file. * tests/test-rmdir.h (test_rmdir_func): Add parameter. * tests/test-rmdir.c (main): Adjust caller. * tests/test-unlinkat.c (main): Likewise. Add unlink tests. (unlinker): New helper function. (rmdirat): Enhance check. * modules/rmdir-tests (Depends-on): Add stdbool. * modules/unlink-tests (Depends-on): Likewise. (Files): Add test-unlink.h. * modules/openat-tests (Files): Likewise. (Depends-on): Add unlinkdir. Signed-off-by: Eric Blake <ebb9@byu.net>