krb5_build_principal_va does not allocate the outer krb5_principal,
making it useless for generating krb5_principals which can be freed
with krb5_free_principal. Added krb5_build_principal_alloc_va which
allocates the krb5_principal.
Added krb5int_build_principal_alloc_va which is used by KIM to avoid
code duplication. KIM's kim_identity_create_from_components takes
the first component as an argument because principals with no
components cannot be represented with the KIM UI. Modified KIM
to use this new API.
Commit By: lxs