krb5: export krb5_time_abs for test_time

Function introduced in 8a4ce995 needs to be exported.

lib/krb5/version-script.map

@@ -825,6 +825,7 @@ HEIMDAL_KRB5_2.0 {
 		krb5_init_creds_free;
 
 		# testing
+		krb5_time_abs;
 		_krb5_aes_cts_encrypt;
 		_krb5_n_fold;
 		_krb5_expand_default_cc_name;