Fix CI errors on Ubuntu 24.04

Fix CI errors on Ubuntu 24.04

Supress a warning in the parser generated by Bison from x-deltat.y.
Convert krb5_ldap_get_age() to use a prototype.  Fix memory leaks in
the ASN.1 tests.  Check errflg after argument parsing in kdc5_hammer.

Pin the linux-clang job to Ubuntu 22.04 until we can work around an
llvm-symbolizer issue which causes test suite failures.