Log Message:
Update ruby-rdtool package to 0.6.13.

= CHANGES
:0.6.13
  * now tabs are expanded into spaces.
  * removed <p> for TextBlock in DescListItem when the TextBlock is only
    element of ListItem.
  * a line of `---\n' are now regarded as Verbatim (or TextBlock).
  * changed style of HTML anchors from `label:' to `label-'.
  * fixed rd2man for better support of multiple paragraphs.
  * fixed some bugs.
:0.6.12
  * fixed some bugs.