- Fix build with Kerberbos5 on 8.0 and 9.0 which have new Heimdal
- A similar fix will be required for repocopies of older Postfix versions as well as postfix-current; I will work on those later this week

Fix: Patch is attached; tested on 7.2, 8.0 and 9.0.

How-To-Repeat: - Set WITH_SASLKRB5=true in environment and try building mail/postfix; you will see:
/usr/lib/libkrb5.so: undefined reference to `hx509_certs_init'
/usr/lib/libkrb5.so: undefined reference to `hx509_cert_get_serialnumber'
/usr/lib/libkrb5.so: undefined reference to `hx509_cert_find_subjectAltName_otherName'
/usr/lib/libkrb5.so: undefined reference to `hx509_certs_find'
/usr/lib/libkrb5.so: undefined reference to `hx509_verify_attach_anchors'
/usr/lib/libkrb5.so: undefined reference to `hx509_query_alloc'
/usr/lib/libkrb5.so: undefined reference to `hx509_get_error_string'
/usr/lib/libkrb5.so: undefined reference to `hx509_cms_unenvelope'
/usr/lib/libkrb5.so: undefined reference to `hx509_lock_add_password'
/usr/lib/libkrb5.so: undefined reference to `hx509_revoke_init'
/usr/lib/libkrb5.so: undefined reference to `hx509_verify_hostname'
/usr/lib/libkrb5.so: undefined reference to `hx509_cms_unwrap_ContentInfo'

... so on and so forth.