message: Set PO-Revision-Date for PO files created from POT
  It was already set when _saving_ the file, but that's too late. We need
  to set it to a valid value at creation time, otherwise Validate on not
  yet saved file would throw an error.
diff: @@ -493,6 +493,9 @@ void Catalog::CreateNewHeader(const Catalog::HeaderData& pot_header)
  HeaderData &dt = Header();
  dt = pot_header;
  + if ( !dt.RevisionDate.empty() )
  + dt.RevisionDate = GetCurrentTimeString();
  +
  // UTF-8 should be used by default no matter what the POT uses
  dt.Charset = "UTF-8";
  