[v9_9] fix test errors

- require 5.006_001
- cut off the least significant figures of rrsig dates before
  comparison to avoid integer overflow

(cherry picked from commit 5efcb3a3e2)

bin/tests/system/formerr/formerr.pl

@@ -45,7 +45,7 @@
 #
 # XXX: Doesn't support IPv6 yet
 
-require 5.006.001;
+require 5.006_001;
 
 use strict;
 use Getopt::Std;