WikiBugs/MoreVerboseSubValidId

Inspired and thanks to CWICK, adds explanations to the last two cases without them.

sub ValidId {
...
  if (!($id =~ m|^$FreeLinkPattern$|)) {
    - return Ts('Invalid Page %s', $id);
    + return Ts('Invalid Page %s  (does not match FreeLinkPattern', $id);
  }
...
  } else {
    if (!($id =~ /^$LinkPattern$/)) {
      - return Ts('Invalid Page %s', $id);
      + return Ts('Invalid Page %s (does not match LinkPattern)', $id);
    }
...

--JuanmaMP