New execute_array() semantics break existing code

[Brian McCauley]

$sth->execute_array({ ArrayTupleStatus => [] }, "FOO", [] );
...used to be a no-op and now is equvalent to...
$sth->execute ( "FOO", undef);
IMHO there is no good reason for this.  If I pass an empty array I 
expect nothing to happen. I have a largish codebase based on this quite 
resonable expectation.

     foreach (keys(%hash_of_arrays)) {
        my $ary = $hash_of_arrays{$_};
        my $len = (ref $ary eq 'ARRAY') ? @$ary : 1;
        $maxlen = $len if $len > $maxlen;
     }
Should be...
     foreach (values(%hash_of_arrays)) {
        $maxlen = @$_ if ref eq 'ARRAY' && @$_ > $maxlen;
     }